Plants having increased tolerance to herbicides

ABSTRACT

The present invention refers to a method for controlling undesired vegetation at a plant cultivation site, the method comprising the steps of providing, at said site, a plant that comprises at least one nucleic acid comprising a nucleotide sequence encoding a wild-type or a mutated protoporphyrinogen oxidase (PPO) which is resistant or tolerant to a benzoxazinone-derivative herbicide by applying to said site an effective amount of said herbicide. The invention further refers to plants comprising wild-type or mutated PPO enzymes, and methods of obtaining such plants.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/918,212, filed Jun. 14, 2013, which claims the benefit of U.S.Provisional Application No. 61/661,364, filed Jun. 19, 2012. The entirecontents of the aforementioned applications are incorporated herein byreference.

REFERENCE TO SEQUENCE LISTING SUBMITTED VIA EFS-WEB

This application was filed electronically via EFS-Web and includes anelectronically submitted sequence listing in .txt format. The .txt filecontains a sequence listing entitled “73943-CON_Seqlisting” created onJun. 26, 2018, and is 154,031 bytes in size. The sequence listingcontained in this .txt file is part of the specification and is herebyincorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates in general to methods for conferring onplants agricultural level tolerance to a herbicide. Particularly, theinvention refers to plants having an increased tolerance to“benzoxazinone-derivative” herbicides. More specifically, the presentinvention relates to methods and plants obtained by mutagenesis andcross-breeding and transformation that have an increased tolerance to“benzoxazinone-derivative” herbicides.

BACKGROUND OF THE INVENTION

Herbicides that inhibit protoporphyrinogen oxidase (hereinafter referredto as Protox or PPO; EC:1.3.3.4), a key enzyme in the biosynthesis ofprotoporphyrin IX, have been used for selective weed control since the1960s. PPO catalyzes the last common step in chlorophyll and hemebiosynthesis which is the oxidation of protoporphyrinogen IX toprotoporphyrin IX. (Matringe et al. 1989. Biochem. 1. 260: 231).PPO-inhibiting herbicides include many different structural classes ofmolecules (Duke et al. 1991. Weed Sci. 39: 465; Nandihalli et al. 1992.Pesticide Biochem. Physiol. 43: 193; Matringe et al. 1989. FEBS Lett.245: 35; Yanase and Andoh. 1989. Pesticide Biochem. Physiol. 35: 70).These herbicidal compounds include the diphenylethers {e.g. lactofen,(+−)-2-ethoxy-1-methyl-2-oxoethyl5-{2-chloro-4-(trifluoromethyl)phenoxy}-2-nitrobenzoate; acifluorfen,5-{2-chloro-4-(trifluoromethyl)phenoxy}-2-nitrobenzoic acid; its methylester; or oxyfluorfen,2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluorobenzene)}, oxidiazoles,(e.g. oxidiazon,3-{2,4-dichloro-5-(1-methylethoxy)phenyl}-5-(1,1-dimethylethyl)-1,3,4-oxadiazol-2-(3H)-one),cyclic imides (e.g. S-23142,N-(4-chloro-2-fluoro-5-propargyloxyphenyl)-3,4,5,6-tetrahydrophthalimide;chlorophthalim, N-(4-chlorophenyl)-3,4,5,6-tetrahydrophthalimide),phenyl pyrazoles (e.g. TNPP-ethyl, ethyl2-{1-(2,3,4-trichlorophenyl)-4-nitropyrazolyl-5-oxy}propionate; M&B39279), pyridine derivatives (e.g. LS 82-556), and phenopylate and itsO-phenylpyrrolidino- and piperidinocarbamate analogs. Many of thesecompounds competitively inhibit the normal reaction catalyzed by theenzyme, apparently acting as substrate analogs.

Application of PPO-inhibiting herbicides results in the accumulation ofprotoporphyrinogen IX in the chloroplast and mitochondria, which isbelieved to leak into the cytosol where it is oxidized by a peroxidase.When exposed to light, protoporphyrin IX causes formation of singletoxygen in the cytosol and the formation of other reactive oxygenspecies, which can cause lipid peroxidation and membrane disruptionleading to rapid cell death (Lee et al. 1993. Plant Physiol. 102: 881).

Not all PPO enzymes are sensitive to herbicides which inhibit plant PPOenzymes. Both the Escherichia coli and Bacillus subtilis PPO enzymes(Sasarmen et al. 1993. Can. J. Microbiol. 39: 1155; Dailey et al. 1994.J. Biol. Chem. 269: 813) are resistant to these herbicidal inhibitors.Mutants of the unicellular alga Chlamydomonas reinhardtii resistant tothe phenylimide herbicide S-23142 have been reported (Kataoka et al.1990. J. Pesticide Sci. 15: 449; Shibata et al. 1992. In Research inPhotosynthesis, Vol. III, N. Murata, ed. Kluwer:Netherlands. pp.567-70). At least one of these mutants appears to have an altered PPOactivity that is resistant not only to the herbicidal inhibitor on whichthe mutant was selected, but also to other classes of protox inhibitors(Oshio et al. 1993. Z. Naturforsch. 48c: 339; Sato et al. 1994. In ACSSymposium on Porphyric Pesticides, S. Duke, ed. ACS Press: Washington,D.C.). A mutant tobacco cell line has also been reported that isresistant to the inhibitor S-21432 (Che et al. 1993. Z. Naturforsch.48c: 350). Auxotrophic E. coli mutants have been used to confirm theherbicide resistance of cloned plant PPOs.

Three main strategies are available for making plants tolerant toherbicides, i.e. (1) detoxifying the herbicide with an enzyme whichtransforms the herbicide, or its active metabolite, into non-toxicproducts, such as, for example, the enzymes for tolerance to bromoxynilor to basta (EP242236, EP337899); (2) mutating the target enzyme into afunctional enzyme which is less sensitive to the herbicide, or to itsactive metabolite, such as, for example, the enzymes for tolerance toglyphosate (EP293356, Padgette S. R. et al., J. Biol. Chem., 266, 33,1991); or (3) overexpressing the sensitive enzyme so as to producequantities of the target enzyme in the plant which are sufficient inrelation to the herbicide, in view of the kinetic constants of thisenzyme, so as to have enough of the functional enzyme available despitethe presence of its inhibitor. The third strategy was described forsuccessfully obtaining plants which were tolerant to PPO inhibitors (seee.g. U.S. Pat. No. 5,767,373 or 5,939,602, and patent family membersthereof.). In addition, US 2010/0100988 and WO 2007/024739 disclosesnucleotide sequences encoding amino acid sequences having enzymaticactivity such that the amino acid sequences are resistant to PPOinhibitor herbicidal chemicals, in particular 3-phenyluracil inhibitorspecific PPO mutants.

To date, the prior art has not described benzoxazinone-derivativeherbicide tolerant plants containing at least one wild-type or mutatedPPO nucleic acid. Nor has the prior art describedbenzoxazinone-derivative herbicide tolerant crop plants containingmutations on genomes other than the genome from which the PPO gene isderived. Therefore, what is needed in the art is the identification ofbenzoxazinone-derivative herbicide tolerance genes from additionalgenomes and species. What are also needed in the art are crop plants andcrop plants having increased tolerance to herbicides such asbenzoxazinone-derivative herbicide and containing at least one wildtypeand/or mutated PPO nucleic acid. Also needed are methods for controllingweed growth in the vicinity of such crop plants or crop plants. Thesecompositions and methods would allow for the use of spray overtechniques when applying herbicides to areas containing crop plants orcrop plants.

SUMMARY OF THE INVENTION

The problem is solved by the present invention which refers to a methodfor controlling undesired vegetation at a plant cultivation site, themethod comprising the steps of:

-   -   a) providing, at said site, a plant that comprises at least one        nucleic acid comprising a nucleotide sequence encoding a wild        type protoporphyrinogen oxidase (PPO) or a mutated        protoporphyrinogen oxidase (mut-PPO) which is resistant or        tolerant to a benzoxazinone-derivative herbicide,    -   b) applying to said site an effective amount of said herbicide.

In addition, the present invention refers to a method for identifying abenzoxazinone-derivative herbicide by using a wild-type or mut-PPOencoded by a nucleic acid which comprises the nucleotide sequence of SEQID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33,35, 37, 39, 41, 43, or 45, or a variant thereof.

Said method comprises the steps of:

-   -   a) generating a transgenic cell or plant comprising a nucleic        acid encoding a mut-PPO, wherein the mut-PPO is expressed;    -   b) applying a benzoxazinone-derivative herbicide to the        transgenic cell or plant of a) and to a control cell or plant of        the same variety;    -   c) determining the growth or the viability of the transgenic        cell or plant and the control cell or plant after application of        said test compound, and    -   d) selecting test compounds which confer reduced growth to the        control cell or plant as compared to the growth of the        transgenic cell or plant.

Another object refers to a method of identifying a nucleotide sequenceencoding a mut-PPO which is resistant or tolerant to abenzoxazinone-derivative herbicide, the method comprising:

-   -   a) generating a library of mut-PPO-encoding nucleic acids,    -   b) screening a population of the resulting mut-PPO-encoding        nucleic acids by expressing each of said nucleic acids in a cell        or plant and treating said cell or plant with a        benzoxazinone-derivative herbicide,    -   c) comparing the benzoxazinone-derivative herbicide-tolerance        levels provided by said population of mut-PPO encoding nucleic        acids with the benzoxazinone-derivative herbicide-tolerance        level provided by a control PPO-encoding nucleic acid,    -   d) selecting at least one mut-PPO-encoding nucleic acid that        provides a significantly increased level of tolerance to a        benzoxazinone-derivative herbicide as compared to that provided        by the control PPO-encoding nucleic acid.

In a preferred embodiment, the mut-PPO-encoding nucleic acid selected instep d) provides at least 2-fold as much tolerance to abenzoxazinone-derivative herbicide as compared to that provided by thecontrol PPO-encoding nucleic acid.

The resistance or tolerance can be determined by generating a transgenicplant comprising a nucleic acid sequence of the library of step a) andcomparing said transgenic plant with a control plant.

Another object refers to a method of identifying a plant or algaecontaining a nucleic acid encoding a mut-PPO which is resistant ortolerant to a benzoxazinone-derivative herbicide, the method comprising:

-   -   a) identifying an effective amount of a benzoxazinone-derivative        herbicide in a culture of plant cells or green algae.    -   b) treating said plant cells or green algae with a mutagenizing        agent,    -   c) contacting said mutagenized cells population with an        effective amount of benzoxazinone-derivative herbicide,        identified in a),    -   d) selecting at least one cell surviving these test conditions,    -   e) PCR-amplification and sequencing of PPO genes from cells        selected in d) and comparing such sequences to wild-type PPO        gene sequences, respectively.

In a preferred embodiment, the mutagenizing agent isethylmethanesulfonate.

Another object refers to an isolated nucleic acid encoding a mut-PPO,the nucleic acid comprising the sequence of SEQ ID NO: 1, 3, 5, 7, 9,11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, or45, or a variant thereof, as defined hereinafter.

Another object refers to an isolated mut-PPO polypeptide, thepolypeptide comprising the sequence set forth in SEQ ID NO: 2, 4, 6, 8,10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44,or 46, a variant, derivative, orthologue, paralogue or homologuethereof, as defined hereinafter.

In a preferred embodiment, the nucleic acid being identifiable by amethod as defined above.

In another embodiment, the invention refers to a plant cell transformedby a wild-type or a mut-PPO nucleic acid or a plant which has beenmutated to obtain a plant expressing, preferably over-expressing awild-type or a mut-PPO nucleic acid, wherein expression of the nucleicacid in the plant cell results in increased resistance or tolerance to abenzoxazinone-derivative herbicide as compared to a wild type variety ofthe plant cell.

In another embodiment, the invention refers to a plant comprising aplant cell according to the present invention, wherein expression of thenucleic acid in the plant results in the plant's increased resistance tobenzoxazinone-derivative herbicide as compared to a wild type variety ofthe plant.

The plants of the present invention can be transgenic or non-transgenic.

Preferably, the expression of the nucleic acid of the invention in theplant results in the plant's increased resistance tobenzoxazinone-derivative herbicide as compared to a wild type variety ofthe plant.

In another embodiment, the invention refers to a seed produced by atransgenic plant comprising a plant cell of the present invention,wherein the seed is true breeding for an increased resistance to abenzoxazinone-derivative herbicide as compared to a wild type variety ofthe seed.

In another embodiment, the invention refers to a method of producing atransgenic plant cell with an increased resistance to abenzoxazinone-derivative herbicide as compared to a wild type variety ofthe plant cell comprising, transforming the plant cell with anexpression cassette comprising a wild-type or a mut-PPO nucleic acid.

In another embodiment, the invention refers to a method of producing atransgenic plant comprising, (a) transforming a plant cell with anexpression cassette comprising a wild-type or a mut-PPO nucleic acid,and (b) generating a plant with an increased resistance tobenzoxazinone-derivative herbicide from the plant cell.

Preferably, the expression cassette further comprises a transcriptioninitiation regulatory region and a translation initiation regulatoryregion that are functional in the plant.

In another embodiment, the invention relates to using the mut-PPO of theinvention as selectable marker. The invention provides a method ofidentifying or selecting a transformed plant cell, plant tissue, plantor part thereof comprising a) providing a transformed plant cell, planttissue, plant or part thereof, wherein said transformed plant cell,plant tissue, plant or part thereof comprises an isolated nucleic acidencoding a mut-PPO polypeptide of the invention as describedhereinafter, wherein the polypeptide is used as a selection marker, andwherein said transformed plant cell, plant tissue, plant or part thereofmay optionally comprise a further isolated nucleic acid of interest; b)contacting the transformed plant cell, plant tissue, plant or partthereof with at least one benzoxazinone-derivative inhibiting compound;c) determining whether the plant cell, plant tissue, plant or partthereof is affected by the inhibitor or inhibiting compound; and d)identifying or selecting the transformed plant cell, plant tissue, plantor part thereof.

The invention is also embodied in purified mut-PPO proteins that containthe mutations described herein, which are useful in molecular modelingstudies to design further improvements to herbicide tolerance. Methodsof protein purification are well known, and can be readily accomplishedusing commercially available products or specially designed methods, asset forth for example, in Protein Biotechnology, Walsh and Headon(Wiley, 1994).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an amino acid sequence alignment of Amaranthus tuberculatus(A. tuberculatus), Amaranthus tuberculatus resistant (A.tuberculatus_R), Arabidopsis thaliana long (A. thaliana_2), Spinaciaoleracea short (S. oleracea_2), Nicotiana tabacum short (N. tabacum_2),Glycine max (Glycine_max), Arabidopsis thaliana short (A. thaliana_1),Nicotiana tabacum long (N. tabacum_1), Chlamydomonas reinhardtii long(C. reinhardtii_1), Zea mays (Z. mays), Oryza sativa (O. sativa_1),Solanum tuberosum (S. tuberosum), Cucumis sativus (C. sativus),Cichorium intybus (C. intybus_1), Spinacia oleracea long (S.oleracea_1), Polytomella sp. Pringsheim 198.80 (Polytomella) PPOsequences. Conserved regions are indicated in light grey, grey andblack.

FIG. 2A and FIG. 2B show the selection of Chlamydomonas reinhardtiistrains resistant to benzoxazinone-derivative 1.a.35 herbicide. FIG. 2AMutagenized cells plated on solid medium without a selecting agent. FIG.2B Mutagenized cells plated on solid medium containing 1×10⁻⁷ Mbenzoxazinone-derivative I.a.35. Cells which are resistant to thebenzoxazinone-derivative herbicide form colonies (circled and numbered31 and 32), while susceptible cells do not grow. The higher number ofcolonies on plate A (FIG. 2A) as compared to B (FIG. 2B), indicate thatthe colonies on plate B are resistant to benzoxazinone-derivativeI.a.35.

FIG. 3A and FIG. 3B show growth-characteristics of selectedChlamydomonas reinhardtii strains as seen in FIG. 2A and FIG. 2B,resistant to benzoxazinone-derivative 1.a.35 herbicide. FIG. 3ADose-response curve of Wild-type cells treated withbenzoxazinone-derivative I.a.35 with respective IC₅₀. FIG. 3BDose-response curve of mutagenized cells (strain 17) treated withbenzoxazinone-derivative I.a.35 with respective IC₅₀. Strain 17 (FIG.3B), resistant to the benzoxazinone-derivative 1.a.35 herbicide, showsmuch lower IC₅₀, compared to Wild-type cells.

KEY TO SEQUENCE LISTING

TABLE 1 SEQ. ID NO: Description Organism Gene Accession No: 1 PPOnucleic acid Amaranthus PPX2L_WC DQ386114 2 PPO amino acid AmaranthusABD52326 3 PPO nucleic acid Amaranthus PPX2L_AC DQ386117 4 PPO aminoacid Amaranthus ABD52329 5 PPO nucleic acid Amaranthus PPX2L_CC_RDQ386118 6 PPO amino acid Amaranthus ABD52330 7 PPO nucleic acidAmaranthus PPX2L_AC_R DQ386116 8 PPO amino acid Amaranthus ABD52328 9PPO nucleic acid Arabidopsis PPX AB007650 10 PPO amino acid ArabidopsisBAB08301 11 PPO nucleic acid Nicotiana ppxI AF044128 12 PPO amino acidNicotiana AAD02290 13 PPO nucleic acid Cichorium PPX1 AF160961 14 PPOamino acid Cichorium AF160961_1 15 PPO nucleic acid Spinacia SO-POX1AB029492 16 PPO amino acid Spinacia BAA96808 17 PPO nucleic acidSpinacia SO-POX2 AB046993 18 PPO amino acid Spinacia BAB60710 19 PPOnucleic acid Solanum PPOX AJ225107 20 PPO amino acid Solanum CAA12400 21PPO nucleic acid Zea ZM_BFc0091B03 BT063659 22 PPO amino acid ZeaACN28356 23 PPO nucleic acid Zea prpo2 NM_001111534 24 PPO amino acidZea NP_001105004 25 PPO nucleic acid Chlamydomonas Ppx1 AF068635 26 PPOamino acid Chlamydomonas AAC79685 27 PPO nucleic acid Polytomella PPOAF332964 28 PPO amino acid Polytomella AF332964_1 29 PPO nucleic acidSorghum Hyp. Protein XM_002446665 30 PPO amino acid Sorghum XP_00244671031 PPO nucleic acid Chlorella 32 PPO amino acid Chlorella 51538 33 PPOnucleic acid Oryza PPOX1 AB057771 34 PPO amino acid Oryza BAB39760 35PPO nucleic acid Amaranthus PPX2 DQ386113 36 PPO amino acid AmaranthusABD52325 37 PPO nucleic acid Arabidopsis PPOX NM_178952 38 PPO aminoacid Arabidopsis NP_849283 39 PPO nucleic acid Nicotiana ppxII AF04412940 PPO amino acid Nicotiana AAD02291 41 PPO nucleic acid Glycine hemGAB025102 42 PPO amino acid Glycine BAA76348 43 PPO nucleic acid CucumisCsPPO AB512426 44 PPO amino acid Cucumis BAH84864.1 45 PPO nucleic acidOryza Hyp. Protein AL606613 46 PPO amino acid Oryza CAE01661

DETAILED DESCRIPTION

The articles “a” and “an” are used herein to refer to one or more thanone (i.e., to at least one) of the grammatical object of the article. Byway of example, “an element” means one or more elements.

As used herein, the word “comprising,” or variations such as “comprises”or “comprising,” will be understood to imply the inclusion of a statedelement, integer or step, or group of elements, integers or steps, butnot the exclusion of any other element, integer or step, or group ofelements, integers or steps.

The present invention refers to a method for controlling undesiredvegetation at a plant cultivation site, the method comprising the stepsof:

-   -   a) providing, at said site, a plant that comprises at least one        nucleic acid comprising a nucleotide sequence encoding a        wild-type protoporphyrinogen oxidase or a mutated        protoporphyrinogen oxidase (mut-PPO) which is resistant or        tolerant to a benzoxazinone-derivative herbicide,    -   b) applying to said site an effective amount of said herbicide.

The term “control of undesired vegetation” is to be understood asmeaning the killing of weeds and/or otherwise retarding or inhibitingthe normal growth of the weeds. Weeds, in the broadest sense, areunderstood as meaning all those plants which grow in locations wherethey are undesired. The weeds of the present invention include, forexample, dicotyledonous and monocotyledonous weeds. Dicotyledonous weedsinclude, but are not limited to, weeds of the genera: Sinapis, Lepidium,Galium, Stellaria, Matricaria, Anthemis, Galinsoga, Chenopodium, Urtica,Senecio, Amaranthus, Portulaca, Xanthium, Convolvulus, Ipomoea,Polygonum, Sesbania, Ambrosia, Cirsium, Carduus, Sonchus, Solanum,Rorippa, Rotala, Lindernia, Lamium, Veronica, Abutilon, Emex, Datura,Viola, Galeopsis, Papaver, Centaurea, Trifolium, Ranunculus, andTaraxacum. Monocotyledonous weeds include, but are not limited to, weedsof the genera: Echinochloa, Setaria, Panicum, Digitaria, Phleum, Poa,Festuca, Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum,Agropyron, Cynodon, Monochoria, Fimbristyslis, Sagittaria, Eleocharis,Scirpus, Paspalum, Ischaemum, Sphenoclea, Dactyloctenium, Agrostis,Alopecurus, and Apera. In addition, the weeds of the present inventioncan include, for example, crop plants that are growing in an undesiredlocation. For example, a volunteer maize plant that is in a field thatpredominantly comprises soybean plants can be considered a weed, if themaize plant is undesired in the field of soybean plants.

The term “plant” is used in its broadest sense as it pertains to organicmaterial and is intended to encompass eukaryotic organisms that aremembers of the Kingdom Plantae, examples of which include but are notlimited to vascular plants, vegetables, grains, flowers, trees, herbs,bushes, grasses, vines, ferns, mosses, fungi and algae, etc., as well asclones, offsets, and parts of plants used for asexual propagation (e.g.cuttings, pipings, shoots, rhizomes, underground stems, clumps, crowns,bulbs, corms, tubers, rhizomes, plants/tissues produced in tissueculture, etc.). The term “plant” further encompasses whole plants,ancestors and progeny of the plants and plant parts, including seeds,shoots, stems, leaves, roots (including tubers), flowers, florets,fruits, pedicles, peduncles, stamen, anther, stigma, style, ovary,petal, sepal, carpel, root tip, root cap, root hair, leaf hair, seedhair, pollen grain, microspore, cotyledon, hypocotyl, epicotyl, xylem,phloem, parenchyma, endosperm, a companion cell, a guard cell, and anyother known organs, tissues, and cells of a plant, and tissues andorgans, wherein each of the aforementioned comprise the gene/nucleicacid of interest. The term “plant” also encompasses plant cells,suspension cultures, callus tissue, embryos, meristematic regions,gametophytes, sporophytes, pollen and microspores, again wherein each ofthe aforementioned comprises the gene/nucleic acid of interest.

Plants that are particularly useful in the methods of the inventioninclude all plants which belong to the superfamily Viridiplantae, inparticular monocotyledonous and dicotyledonous plants including fodderor forage legumes, ornamental plants, food crops, trees or shrubsselected from the list comprising Acer spp., Actinidia spp., Abelmoschusspp., Agave sisalana, Agropyron spp., Agrostis stolonifera, Allium spp.,Amaranthus spp., Ammophila arenaria, Ananas comosus, Annona spp., Apiumgraveolens, Arachis spp, Artocarpus spp., Asparagus officinalis, Avenaspp. (e.g. Avena sativa, Avena fatua, Avena byzantina, Avena fatua var.sativa, Avena hybrida), Averrhoa carambola, Bambusa sp., Benincasahispida, Bertholletia excelsea, Beta vulgaris, Brassica spp. (e.g.Brassica napus, Brassica rapa ssp. [canola, oilseed rape, turnip rape]),Cadaba farinosa, Camellia sinensis, Canna indica, Cannabis sativa,Capsicum spp., Carex elata, Carica papaya, Carissa macrocarpa, Caryaspp., Carthamus tinctorius, Castanea spp., Ceiba pentandra, Cichoriumendivia, Cinnamomum spp., Citrullus lanatus, Citrus spp., Cocos spp.,Coffea spp., Colocasia esculenta, Cola spp., Corchorus sp., Coriandrumsativum, Corylus spp., Crataegus spp., Crocus sativus, Cucurbita spp.,Cucumis spp., Cynara spp., Daucus carota, Desmodium spp., Dimocarpuslongan, Dioscorea spp., Diospyros spp., Echinochloa spp., Elaeis (e.g.Elaeis guineensis, Elaeis oleifera), Eleusine coracana, Eragrostis tef,Erianthus sp., Eriobotrya japonica, Eucalyptus sp., Eugenia uniflora,Fagopyrum spp., Fagus spp., Festuca arundinacea, Ficus carica,Fortunella spp., Fragaria spp., Ginkgo biloba, Glycine spp. (e.g.Glycine max, Soja hispida or Soja max), Gossypium hirsutum, Helianthusspp. (e.g. Helianthus annuus), Hemerocallis fulva, Hibiscus spp.,Hordeum spp. (e.g. Hordeum vulgare), Ipomoea batatas, Juglans spp.,Lactuca sativa, Lathyrus spp., Lens culinaris, Linum usitatissimum,Litchi chinensis, Lotus spp., Luffa acutangula, Lupinus spp., Luzulasylvatica, Lycopersicon spp. (e.g. Lycopersicon esculentum, Lycopersiconlycopersicum, Lycopersicon pyriforme), Macrotyloma spp., Malus spp.,Malpighia emarginata, Mammea americana, Mangifera indica, Manihot spp.,Manilkara zapota, Medicago sativa, Melilotus spp., Mentha spp.,Miscanthus sinensis, Momordica spp., Morus nigra, Musa spp., Nicotianaspp., Olea spp., Opuntia spp., Ornithopus spp., Oryza spp. (e.g. Oryzasativa, Oryza latifolia), Panicum miliaceum, Panicum virgatum,Passiflora edulis, Pastinaca sativa, Pennisetum sp., Persea spp.,Petroselinum crispum, Phalaris arundinacea, Phaseolus spp., Phleumpratense, Phoenix spp., Phragmites australis, Physalis spp., Pinus spp.,Pistacia vera, Pisum spp., Poa spp., Populus spp., Prosopis spp., Prunusspp., Psidium spp., Punica granatum, Pyrus communis, Quercus spp.,Raphanus sativus, Rheum rhabarbarum, Ribes spp., Ricinus communis, Rubusspp., Saccharum spp., Salix sp., Sambucus spp., Secale cereale, Sesamumspp., Sinapis sp., Solanum spp. (e.g. Solanum tuberosum, Solanumintegrifolium or Solanum lycopersicum), Sorghum bicolor, Spinacia spp.,Syzygium spp., Tagetes spp., Tamarindus indica, Theobroma cacao,Trifolium spp., Tripsacum dactyloides, Triticosecale rimpaui, Triticumspp. (e.g. Triticum aestivum, Triticum durum, Triticum turgidum,Triticum hybernum, Triticum macha, Triticum sativum, Triticum monococcumor Triticum vulgare), Tropaeolum minus, Tropaeolum majus, Vacciniumspp., Vicia spp., Vigna spp., Viola odorata, Vitis spp., Zea mays,Zizania palustris, Ziziphus spp., amaranth, artichoke, asparagus,broccoli, Brussels sprouts, cabbage, canola, carrot, cauliflower,celery, collard greens, flax, kale, lentil, oilseed rape, okra, onion,potato, rice, soybean, strawberry, sugar beet, sugar cane, sunflower,tomato, squash, tea and algae, amongst others. According to a preferredembodiment of the present invention, the plant is a crop plant. Examplesof crop plants include inter alia soybean, sunflower, canola, alfalfa,rapeseed, cotton, tomato, potato or tobacco. Further preferably, theplant is a monocotyledonous plant, such as sugarcane. Furtherpreferably, the plant is a cereal, such as rice, maize, wheat, barley,millet, rye, sorghum or oats.

In a preferred embodiment, the plant has been previously produced by aprocess comprising recombinantly preparing a plant by introducing andover-expressing a wild-type or mut-PPO transgene, as described ingreater detail hereinafter.

In another preferred embodiment, the plant has been previously producedby a process comprising in situ mutagenizing plant cells, to obtainplant cells which express a mut-PPO.

As disclosed herein, the nucleic acids of the invention find use inenhancing the herbicide tolerance of plants that comprise in theirgenomes a gene encoding a herbicide-tolerant wild-type or mut-PPOprotein. Such a gene may be an endogenous gene or a transgene, asdescribed hereinafter. Additionally, in certain embodiments, the nucleicacids of the present invention can be stacked with any combination ofpolynucleotide sequences of interest in order to create plants with adesired phenotype. For example, the nucleic acids of the presentinvention may be stacked with any other polynucleotides encodingpolypeptides having pesticidal and/or insecticidal activity, such as,for example, the Bacillus thuringiensis toxin proteins (described inU.S. Pat. Nos. 5,366,892; 5,747,450; 5,737,514; 5,723,756; 5,593,881;and Geiser et al (1986) Gene 48: 109). The combinations generated canalso include multiple copies of any one of the polynucleotides ofinterest.

In a particularly preferred embodiment, the plant comprises at least oneadditional heterologous nucleic acid comprising a nucleotide sequenceencoding a herbicide tolerance enzyme selected, for example, from thegroup consisting of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS),Glyphosate acetyl transferase (GAT), Cytochrome P450, phosphinothricinacetyltransferase (PAT), Acetohydroxyacid synthase (AHAS; EC 4.1.3.18,also known as acetolactate synthase or ALS), hydroxyphenyl pyruvatedioxygenase (HPPD), Phytoene desaturase (PD) and dicamba degradingenzymes as disclosed in WO 02/068607, or phenoxyaceticacid- andphenoxypropionicacid-derivative degrading enzymes as disclosed in WO2008141154 or WO 2005107437.

Generally, the term “herbicide” is used herein to mean an activeingredient that kills, controls or otherwise adversely modifies thegrowth of plants. The preferred amount or concentration of the herbicideis an “effective amount” or “effective concentration.” By “effectiveamount” and “effective concentration” is intended an amount andconcentration, respectively, that is sufficient to kill or inhibit thegrowth of a similar, wild-type, plant, plant tissue, plant cell, or hostcell, but that said amount does not kill or inhibit as severely thegrowth of the herbicide-resistant plants, plant tissues, plant cells,and host cells of the present invention. Typically, the effective amountof a herbicide is an amount that is routinely used in agriculturalproduction systems to kill weeds of interest. Such an amount is known tothose of ordinary skill in the art. Herbicidal activity is exhibited bybenzoxazinone-derivative herbicide of the present invention when theyare applied directly to the plant or to the locus of the plant at anystage of growth or before planting or emergence. The effect observeddepends upon the plant species to be controlled, the stage of growth ofthe plant, the application parameters of dilution and spray drop size,the particle size of solid components, the environmental conditions atthe time of use, the specific compound employed, the specific adjuvantsand carriers employed, the soil type, and the like, as well as theamount of chemical applied. These and other factors can be adjusted asis known in the art to promote non-selective or selective herbicidalaction. Generally, it is preferred to apply the benzoxazinone-derivativeherbicide postemergence to relatively immature undesirable vegetation toachieve the maximum control of weeds.

By a “herbicide-tolerant” or “herbicide-resistant” plant, it is intendedthat a plant that is tolerant or resistant to at least one herbicide ata level that would normally kill, or inhibit the growth of, a normal orwild-type plant. By “herbicide-tolerant mut-PPO protein” or“herbicide-resistant mut-PPO protein”, it is intended that such amut-PPO protein displays higher PPO activity, relative to the PPOactivity of a wild-type mut-PPO protein, when in the presence of atleast one herbicide that is known to interfere with PPO activity and ata concentration or level of the herbicide that is known to inhibit thePPO activity of the wild-type mut-PPO protein. Furthermore, the PPOactivity of such a herbicide-tolerant or herbicide-resistant mut-PPOprotein may be referred to herein as “herbicide-tolerant” or“herbicide-resistant” PPO activity.

The “benzoxazinone-derivative herbicide” that are useful to carry outthe present invention encompasses the benzoxazinones of formula I asdepicted in the following:

-   -   wherein    -   R¹ is hydrogen or halogen;    -   R² is halogen;    -   R³ is hydrogen or halogen;    -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl,        C₃-C₆-alkenyl, C₃-C₆-haloalkenyl, C₃-C₆-alkynyl,        C₃-C₆-haloalkynyl, C₁-C₆-alkoxy or C₃-C₆-cycloalkyl-C₁-C₆-alkyl;    -   R⁵ is hydrogen, NH₂, C₁-C₆-alkyl or C₃-C₆-alkynyl;    -   R⁶ is hydrogen or C₁-C₆-alkyl; and    -   W is O or S;    -   Z is O or S.

In another preferred embodiment, the “benzoxazinone-derivativeherbicide” that are useful to carry out the present inventionencompasses the benzoxazinones of formula I as depicted in thefollowing:

A) at least one benzoxazinone of the formula I

-   -   wherein    -   R¹ is hydrogen or halogen;    -   R² is halogen;    -   R³ is hydrogen or halogen;    -   R⁴ is hydrogen, C₁-C₆-alkyl, C₁-C₆-haloalkyl, C₃-C₆-cycloalkyl,        C₃-C₆-alkenyl, C₃-C₆-haloalkenyl, C₃-C₆-alkynyl,        C₃-C₆-haloalkynyl, C₁-C₆-alkoxy or C₃-C₆-cycloalkyl-C₁-C₆-alkyl;    -   R⁵ is hydrogen, NH₂, C₁-C₆-alkyl or C₃-C₆-alkynyl;    -   R⁶ is hydrogen or C₁-C₆-alkyl; and    -   X is O or S;    -   Y is O or S;

and at least one further active compound selected from

B) herbicides of class b1) to b15):

-   -   b1) lipid biosynthesis inhibitors;    -   b2) acetolactate synthase inhibitors (ALS inhibitors);    -   b3) photosynthesis inhibitors;    -   b4) protoporphyrinogen-IX oxidase inhibitors,    -   b5) bleacher herbicides;    -   b6) enolpyruvyl shikimate 3-phosphate synthase inhibitors (EPSP        inhibitors);    -   b7) glutamine synthetase inhibitors;    -   b8) 7,8-dihydropteroate synthase inhibitors (DHP inhibitors);    -   b9) mitose inhibitors;    -   b10) inhibitors of the synthesis of very long chain fatty acids        (VLCFA inhibitors);    -   b11) cellulose biosynthesis inhibitors;    -   b12) decoupler herbicides;    -   b13) auxin herbicides;    -   b14) auxin transport inhibitors; and    -   b15) other herbicides selected from the group consisting of        bromobutide, chlorflurenol, chlorflurenol-methyl, cinmethylin,        cumyluron, dalapon, dazomet, difenzoquat,        difenzoquat-metilsulfate, dimethipin, DSMA, dymron, endothal and        its salts, etobenzanid, flamprop, flamprop-isopropyl,        flamprop-methyl, flamprop-M-isopropyl, flamprop-M-methyl,        flurenol, flurenol-butyl, flurprimidol, fosamine,        fosamine-ammonium, indanofan, indaziflam, maleic hydrazide,        mefluidide, metam, methyl azide, methyl bromide, methyl-dymron,        methyl iodide, MSMA, oleic acid, oxaziclomefone, pelargonic        acid, pyributicarb, quinoclamine, triaziflam, tridiphane and        6-chloro-3-(2-cyclopropyl-6-methylphenoxy)-4-pyridazinol (CAS        499223-49-3) and its salts and esters;

and

C) safeners.

The benzoxazinone-derivative herbicide that are useful for the presentinvention can also be compositions in the form of herbicidally activecrop protection compositions comprising a herbicidally effective amountof an active compound combination comprising at least one benzoxazinoneof formula I and at least one further compound selected from theherbicides B and the safeners C, as defined above, and also at least oneliquid and/or solid carrier and/or one or more surfactants and, ifdesired, one or more further auxiliaries customary for crop protectioncompositions.

Further, benzoxazinone-derivative herbicide that are useful for thepresent invention can also be compositions in the form of a cropprotection composition formulated as a 1-component compositioncomprising an active compound combination comprising at least onebenzoxazinone of formula I and at least one further active compoundselected from the herbicides B and the safeners C, and at least onesolid or liquid carrier and/or one or more surfactants and, if desired,one or more further auxiliaries customary for crop protectioncompositions.

Further, benzoxazinone-derivative herbicide that are useful for thepresent invention can also be compositions in the form of a cropprotection composition formulated as a 2-component compositioncomprising a first component comprising at least one benzoxazinone offormula I, a solid or liquid carrier and/or one or more surfactants, anda second component comprising at least one further active compoundselected from the herbicides B and safeners C, a solid or liquid carrierand/or one or more surfactants, where additionally both components mayalso comprise further auxiliaries customary for crop protectioncompositions.

If the benzoxazinones of formula I as described herein are capable offorming geometrical isomers, for example E/Z isomers, it is possible touse both, the pure isomers and mixtures thereof, in the compositionsaccording to the invention.

If the benzoxazinones of formula I as described herein have one or morecenters of chirality and, as a consequence, are present as enantiomersor diastereomers, it is possible to use both, the pure enantiomers anddiastereomers and their mixtures, in the compositions according to theinvention.

The organic moieties mentioned in the definition of the variables R¹ toR⁶, are—like the term halogen—collective terms for individualenumerations of the individual group members. The term halogen denotesin each case fluorine, chlorine, bromine or iodine. All hydrocarbonchains, i.e. all alkyl, can be straight-chain or branched, the prefixC_(n)-C_(m) denoting in each case the possible number of carbon atoms inthe group.

Examples of such meanings are:

-   -   C₁-C₄-alkyl and also the C₁-C₄-alkyl moieties of        C₃-C₆-cycloalkyl-C₁-C₄-alkyl: for example CH₃, C₂H₅, n-propyl,        and CH(CH₃)₂ n-butyl, CH(CH₃)—C₂H₅, CH₂—CH(CH₃)₂ and C(CH₃)₃;    -   C₁-C₆-alkyl and also the C₁-C₆-alkyl moieties of        C₁-C₆-alkyoxy-C₁-C₆-alkyl: C₁-C₄-alkyl as mentioned above, and        also, for example, n-pentyl, 1-methylbutyl, 2-methylbutyl,        3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, n-hexyl,        1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl,        2-methylpentyl, 3-methylpentyl, 4-methylpentyl,        1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl,        2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl,        1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl,        1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl or        1-ethyl-2-methylpropyl, preferably methyl, ethyl, n-propyl,        1-methylethyl, n-butyl, 1,1-dimethylethyl, n-pentyl or n-hexyl;    -   C₁-C₄-haloalkyl: a C₁-C₄-alkyl radical as mentioned above which        is partially or fully substituted by fluorine, chlorine, bromine        and/or iodine, for example, chloromethyl, dichloromethyl,        trichloromethyl, fluoromethyl, difluoromethyl, trifluoromethyl,        chlorofluoromethyl, dichlorofluoromethyl, chlorodifluoromethyl,        bromomethyl, iodomethyl, 2-fluoroethyl, 2-chloroethyl,        2-bromoethyl, 2-iodoethyl, 2,2-difluoroethyl,        2,2,2-trifluoroethyl, 2-chloro-2-fluoroethyl,        2-chloro-2,2-difluoroethyl, 2,2-dichloro-2-fluoroethyl,        2,2,2-trichloroethyl, pentafluoroethyl, 2-fluoropropyl,        3-fluoropropyl, 2,2-difluoropropyl, 2,3-difluoropropyl,        2-chloropropyl, 3-chloropropyl, 2,3-dichloropropyl,        2-bromopropyl, 3-bromopropyl, 3,3,3-trifluoropropyl,        3,3,3-trichloropropyl, 2,2,3,3,3-pentafluoropropyl,        heptafluoropropyl, a C₁-C₃-haloalkyl radical as mentioned above,        and also, for example, 1-(fluoromethyl)-2-fluoroethyl,        1-(chloromethyl)-2-chloroethyl, 1-(bromomethyl)-2-bromoethyl,        4-fluorobutyl, 4-chlorobutyl, 4-bromobutyl, nonafluorobutyl,        1,1,2,2,-tetrafluoroethyl and        1-trifluoromethyl-1,2,2,2-tetrafluoroethyl;    -   C₁-C₆-haloalkyl: C₁-C₄-haloalkyl as mentioned above, and also,        for example, 5-fluoropentyl, 5-chloropentyl, 5-bromopentyl,        5-iodopentyl, undecafluoropentyl, 6-fluorohexyl, 6-chlorohexyl,        6-bromohexyl, 6-iodohexyl and dodecafluorohexyl;    -   C₃-C₆-cycloalkyl and also the cycloalkyl moieties of        C₃-C₆-cycloalkyl-C₁-C₄-alkyl: monocyclic saturated hydrocarbons        having 3 to 6 ring members, such as cyclopropyl, cyclobutyl,        cyclopentyl and cyclohexyl;    -   C₃-C₆-alkenyl: for example 1-propenyl, 2-propenyl,        1-methylethenyl, 1-butenyl, 2-butenyl, 3-butenyl,        1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-methyl-2-propenyl,        2-methyl-2-propenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl,        4-pentenyl, 1-methyl-1-butenyl, 2-methyl-1-butenyl,        3-methyl-1-butenyl, 1-methyl-2-butenyl, 2-methyl-2-butenyl,        3-methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-3-butenyl,        3-methyl-3-butenyl, 1,1-dimethyl-2-propenyl,        1,2-dimethyl-1-propenyl, 1,2-dimethyl-2-propenyl,        1-ethyl-1-propenyl, 1-ethyl-2-propenyl, 1-hexenyl, 2-hexenyl,        3-hexenyl, 4-hexenyl, 5-hexenyl, 1-methyl-1-pentenyl,        2-methyl-1-pentenyl, 3-methyl-1-pentenyl, 4-methyl-1-pentenyl,        1-methyl-2-pentenyl, 2-methyl-2-pentenyl, 3-methyl-2-pentenyl,        4-methyl-2-pentenyl, 1-methyl-3-pentenyl, 2-methyl-3-pentenyl,        3-methyl-3-pentenyl, 4-methyl-3-pentenyl, 1-methyl-4-pentenyl,        2-methyl-4-pentenyl, 3-methyl-4-pentenyl, 4-methyl-4-pentenyl,        1,1-dimethyl-2-butenyl, 1,1-dimethyl-3-butenyl,        1,2-dimethyl-1-butenyl, 1,2-dimethyl-2-butenyl,        1,2-dimethyl-3-butenyl, 1,3-dimethyl-1-butenyl,        1,3-dimethyl-2-butenyl, 1,3-dimethyl-3-butenyl,        2,2-dimethyl-3-butenyl, 2,3-dimethyl-1-butenyl,        2,3-dimethyl-2-butenyl, 2,3-dimethyl-3-butenyl,        3,3-dimethyl-1-butenyl, 3,3-dimethyl-2-butenyl,        1-ethyl-1-butenyl, 1-ethyl-2-butenyl, 1-ethyl-3-butenyl,        2-ethyl-1-butenyl, 2-ethyl-2-butenyl, 2-ethyl-3-butenyl,        1,1,2-trimethyl-2-propenyl, 1-ethyl-1-methyl-2-propenyl,        1-ethyl-2-methyl-1-propenyl and 1-ethyl-2-methyl-2-propenyl;    -   C₃-C₆-haloalkenyl: a C₃-C₆-alkenyl radical as mentioned above        which is partially or fully substituted by fluorine, chlorine,        bromine and/or iodine, for example 2-chloroprop-2-en-1-yl,        3-chloroprop-2-en-1-yl, 2,3-dichloroprop-2-en-1-yl,        3,3-dichloroprop-2-en-1-yl, 2,3,3-trichloro-2-en-1-yl,        2,3-dichlorobut-2-en-1-yl, 2-bromoprop-2-en-1-yl,        3-bromoprop-2-en-1-yl, 2,3-dibromoprop-2-en-1-yl,        3,3-dibromoprop-2-en-1-yl, 2,3,3-tribromo-2-en-1-yl or        2,3-dibromobut-2-en-1-yl;    -   C₃-C₆-alkynyl: for example 1-propynyl, 2-propynyl, 1-butynyl,        2-butynyl, 3-butynyl, 1-methyl-2-propynyl, 1-pentynyl,        2-pentynyl, 3-pentynyl, 4-pentynyl, 1-methyl-2-butynyl,        1-methyl-3-butynyl, 2-methyl-3-butynyl, 3-methyl-1-butynyl,        1,1-dimethyl-2-propynyl, 1-ethyl-2-propynyl, 1-hexynyl,        2-hexynyl, 3-hexynyl, 4-hexynyl, 5-hexynyl, 1-methyl-2-pentynyl,        1-methyl-3-pentynyl, 1-methyl-4-pentynyl, 2-methyl-3-pentynyl,        2-methyl-4-pentynyl, 3-methyl-1-pentynyl, 3-methyl-4-pentynyl,        4-methyl-1-pentynyl, 4-methyl-2-pentynyl,        1,1-dimethyl-2-butynyl, 1,1-dimethyl-3-butynyl,        1,2-dimethyl-3-butynyl, 2,2-dimethyl-3-butynyl,        3,3-dimethyl-1-butynyl, 1-ethyl-2-butynyl, 1-ethyl-3-butynyl,        2-ethyl-3-butynyl and 1-ethyl-1-methyl-2-propynyl;    -   C₃-C₆-haloalkynyl: a C₃-C₆-alkynyl radical as mentioned above        which is partially or fully substituted by fluorine, chlorine,        bromine and/or iodine, for example 1,1-difluoroprop-2-yn-1-yl,        3-chloroprop-2-yn-1-yl, 3-bromoprop-2-yn-1-yl,        3-iodoprop-2-yn-1-yl, 4-fluorobut-2-yn-1-yl,        4-chlorobut-2-yn-1-yl, 1,1-difluorobut-2-yn-1-yl,        4-iodobut-3-yn-1-yl, 5-fluoropent-3-yn-1-yl,        5-iodopent-4-yn-1-yl, 6-fluorohex-4-yn-1-yl or        6-iodohex-5-yn-1-yl;    -   C₁-C₄-alkoxy and also the C₁-C₄-alkoxy moieties of        hydroxycarbonyl-C₁-C₄-alkoxy, C₁-C₆-alkoxycarbonyl-C₁-C₄-alkoxy:        for example methoxy, ethoxy, propoxy, 1-methylethoxy butoxy,        1-methylpropoxy, 2-methylpropoxy and 1,1-dimethylethoxy;    -   C₁-C₆-alkoxy and also the C₁-C₆-alkoxy moieties of        C₁-C₆-alkoxycarbonyl-C₁-C₄-alkoxy: C₁-C₄-alkoxy as mentioned        above, and also, for example, pentoxy, 1-methylbutoxy,        2-methylbutoxy, 3-methoxylbutoxy, 1,1-dimethylpropoxy,        1,2-dimethylpropoxy, 2,2-dimethylpropoxy, 1-ethylpropoxy,        hexoxy, 1-methylpentoxy, 2-methylpentoxy, 3-methylpentoxy,        4-methylpentoxy, 1,1-dimethylbutoxy, 1,2-dimethylbutoxy,        1,3-dimethylbutoxy, 2,2-dimethylbutoxy, 2,3-dimethylbutoxy,        3,3-dimethylbutoxy, 1-ethylbutoxy, 2-ethylbutoxy,        1,1,2-trimethylpropoxy, 1,2,2-trimethylpropoxy,        1-ethyl-1-methylpropoxy and 1-ethyl-2-methylpropoxy.

According to a preferred embodiment of the invention preference is alsogiven to those benzoxazinone-derivative of formula I, wherein thevariables, either independently of one another or in combination withone another, have the following meanings:

R¹ is hydrogen;

-   -   is also preferably halogen, particularly preferred F or Cl,        especially preferred F;    -   R² is F;    -   R³ is hydrogen or F, preferably hydrogen;        -   is also preferably F;    -   R⁴ is C₃-C₆-alkynyl or C₃-C₆-halolkynyl, preferably C₃-alkynyl        or C₃-halolkynyl, particularly preferred CH₂C≡CH, CH₂C≡CCl or        CH₂C≡CBr;        -   is also preferably C₃-C₆-alkynyl or            C₃-C₆-cycloalkyl-C₁-C₆-alkyl, particularly preferred            propargyl or cyclopropylmethyl;        -   is also preferably C₃-C₆-alkynyl, preferably C₃-alkynyl;            particularly preferred CH₂C≡CH;        -   is also preferably C₃-C₆-halolkynyl, preferably            C₃-halolkynyl, particularly preferred CH₂C≡CCl or CH₂C≡CBr;    -   R⁵ is NH₂, C₁-C₆-Alkyl or C₃-C₆-alkynyl; preferably C₁-C₆-alkyl;        more preferably C₁-C₄-alkyl; most preferably CH₃;    -   R⁶ is C₁-C₆-alkyl; preferably C₁-C₄-alkyl; most preferably CH₃;    -   W is O,        -   is also preferably S;    -   Z is O,        -   is also preferably S.    -   Particular preference is given to benzoxazinones of the formula        I.a (corresponds to formula I wherein R² is F, R⁵ and R⁶ are        CH₃, W is O and Z is S),

wherein the variables R¹, R³, and R⁴ have the meanings, in particularthe preferred meanings, as defined above.

Most preference to the benzoxazinone-derivatives of the formulae I.a.1to I.a.48 of Table A listed below, in which the variables R¹, R³ and R⁴together have the meanings given in one row of Table A (benzoxazinonesI.a.1 to I.a.54); and where the definitions of the variables R¹, R²,R³and R⁴ are of particular importance for the compounds according to theinvention not only in combination with one another but in each case alsoon their own.

TABLE A No. R¹ R³ R⁴ I.a.1. H H H I.a.2. H H CH₃ I.a.3. H H C₂H₅ I.a.4.H H CH₂—C₂H₅ I.a.5. H H CH(CH₃)₂ I.a.6. H H CH₂—CH₂—(CH₃)₂ I.a.7. H HCH₂—CH═CH₂ I.a.8. H H CH₂C≡CH I.a.9. H H CH₂C≡C—Br I.a.10. H F H I.a.11.H F CH₃ I.a.12. H F C₂H₅ I.a.13. H F CH₂—C₂H₅ I.a.14. H F CH(CH₃)₂I.a.15. H F CH₂—CH₂—(CH₃)₂ I.a.16. H F CH₂—CH═CH₂ I.a.17. H F CH₂C≡CHI.a.18. H F CH₂C≡C—Br I.a.19. F H H I.a.20. F H CH₃ I.a.21. F H C₂H₅I.a.22. F H CH₂—C₂H₅ I.a.23. F H CH(CH₃)₂ I.a.24. F H CH₂—CH₂—(CH₃)₂I.a.25. F H CH₂—CH═CH₂ I.a.26. F H CH₂C≡CH I.a.27. F H CH₂C≡C—Br I.a.28.F F H I.a.29. F F CH₃ I.a.30. F F C₂H₅ I.a.31. F F CH₂—C₂H₅ I.a.32. F FCH(CH₃)₂ I.a.33. F F CH₂—CH₂—(CH₃)₂ I.a.34. F F CH₂—CH=CH₂ I.a.35. F FCH₂C≡CH I.a.36. F F CH₂C≡C—Br I.a.37. Cl H H I.a.38. Cl H CH₃ I.a.39. ClH C₂H₅ I.a.40. Cl H CH₂—C₂H₅ I.a.41. Cl H CH(CH₃)₂ I.a.42. Cl HCH₂—CH₂—(CH₃)₂ I.a.43. Cl H CH₂—CH═CH₂ I.a.44. Cl H CH₂C≡CH I.a.45. Cl HCH₂C≡C—Br I.a.46. Cl F H I.a.47. Cl F CH₃ I.a.48. Cl F C₂H₅ I.a.49. Cl FCH₂—C₂H₅ I.a.50. Cl F CH(CH₃)₂ I.a.51. Cl F CH₂—CH₂—(CH₃)₂ I.a.52. Cl FCH₂—CH═CH₂ I.a.53. Cl F CH₂C≡CH I.a.54. Cl F CH₂C≡C—Br

An especially preferred benzoxazinone of the formula I which, ascomponent A, is part of the composition according to the invention, isthe benzoxazinone of formula I.a.35 as defined above

According to a particular preferred embodiment of the invention thecomposition useful for the method of the present invention contains ascomponent A the benzoxazinone of formula I.a.35.

The above described benzoxazinone-derivatives and compositions aredisclosed in detail in the European patent application 09163242.2, inparticular the disclosures on pages 1 to 7 referring to thebezoxazinone-derivatives and their possible substitutents are entirelyincorporated by reference.

The benzoxazinone-derivatives that are useful to carry out the presentinvention are often best applied in conjunction with one or more otherherbicides to obtain control of a wider variety of undesirablevegetation. When used in conjunction with other targeting herbicides,the presently claimed compounds can be formulated with the otherherbicide or herbicides, tank mixed with the other herbicide orherbicides, or applied sequentially with the other herbicide orherbicides.

The herbicidal compounds that are useful to carry out the presentinvention may further be used in conjunction with additional herbicidesto which the crop plant is naturally tolerant, or to which it isresistant via expression of one or more additional transgenes asmentioned supra. Some of the herbicides that can be employed inconjunction with the compounds of the present invention includesulfonamides such as metosulam, flumetsulam, cloransulam-methyl,diclosulam, penoxsulam and florasulam, sulfonylureas such aschlorimuron, tribenuron, sulfometuron, nicosulfuron, chlorsulfuron,amidosulfuron, triasulfuron, prosulfuron, tritosulfuron, thifensulfuron,sulfosulfuron and metsulfuron, imidazolinones such as imazaquin,imazapic, ima-zethapyr, imzapyr, imazamethabenz and imazamox,phenoxyalkanoic acids such as 2,4-D, MCPA, dichlorprop and mecoprop,pyridinyloxyacetic acids such as triclopyr and fluroxypyr, carboxylicacids such as clopyralid, picloram, aminopyralid and dicamba,dinitroanilines such as trifluralin, benefin, benfluralin andpendimethalin, chloroacetanilides such as alachlor, acetochlor andmetolachlor, semicarbazones (auxin transport inhibitors) such aschlorflurenol and diflufenzopyr, aryloxyphenoxypropionates such asfluazifop, haloxyfop, diclofop, clodinafop and fenoxaprop and othercommon herbicides including glyphosate, glufosinate, acifluorfen,bentazon, clomazone, fumiclorac, fluometuron, fomesafen, lactofen,linuron, isoproturon, simazine, norflurazon, paraquat, diuron,diflufenican, picolinafen, cinidon, sethoxydim, tralkoxydim, quinmerac,isoxaben, bromoxynil, metribuzin and mesotrione.

For example, the benzoxazinone-derivative herbicides that are useful tocarry out the present invention can be used in conjunction withglyphosate and glufosinate on glyphosate-tolerant orglufosinate-tolerant crops.

Unless already included in the disclosure above, thebenzoxazinone-derivative herbicides that are useful to carry out thepresent invention can, further, be used in conjunction with compounds:

b1) from the group of the lipid biosynthesis inhibitors:

ACC-herbicides such as alloxydim, alloxydim-sodium, butroxydim,clethodim, clodinafop, clodinafop-propargyl, cycloxydim, cyhalofop,cyhalofop-butyl, diclofop, diclofop-methyl, fenoxaprop,fenoxaprop-ethyl, fenoxaprop-P, fenoxaprop-P-ethyl, fluazifop,fluazifop-butyl, fluazifop-P, fluazifop-P-butyl, haloxyfop,haloxyfop-methyl, haloxyfop-P, haloxyfop-P-methyl, metamifop, pinoxaden,profoxydim, propaquizafop, quizalofop, quizalofop-ethyl,quizalofop-tefuryl, quizalofop-P, quizalofop-P-ethyl,quizalofop-P-tefuryl, sethoxydim, tepraloxydim and tralkoxydim, and nonACC herbicides such as benfuresate, butylate, cycloate, dalapon,dimepiperate, EPIC, esprocarb, ethofumesate, flupropanate, molinate,orbencarb, pebulate, prosulfocarb, TCA, thiobencarb, tiocarbazil,triallate and vernolate; b2) from the group of the ALS inhibitors:

Sulfonylureas such as amidosulfuron, azimsulfuron, bensulfuron,bensulfuron-methyl, chlorimuron, chlorimuron-ethyl, chlorsulfuron,cinosulfuron, cyclosulfamuron, ethametsulfuron, ethametsulfuron-methyl,ethoxysulfuron, flazasulfuron, flucetosulfuron, flupyrsulfuron,flupyrsulfuron-methyl-sodium, foramsulfuron, halosulfuron,halosulfuron-methyl, imazosulfuron, iodosulfuron,iodosulfuron-methyl-sodium, mesosulfuron, metazosulfuron, metsulfuron,metsulfuron-methyl, nicosulfuron, orthosulfamuron, oxasulfuron,primisulfuron, primisulfuron-methyl, propyrisulfuron, prosulfuron,pyrazosulfuron, pyrazosulfuron-ethyl, rimsulfuron, sulfometuron,sulfometuron-methyl, sulfosulfuron, thifensulfuron,thifensulfuron-methyl, triasulfuron, tribenuron, tribenuron-methyl,trifloxysulfuron, triflusulfuron, triflusulfuron-methyl andtritosulfuron, imidazolinones such as imazamethabenz,imazamethabenz-methyl, imazamox, imazapic, imazapyr, imazaquin andimazethapyr, triazolopyrimidine herbicides and sulfonanilides such ascloransulam, cloransulam-methyl, diclosulam, flumetsulam, florasulam,metosulam, penoxsulam, pyrimisulfan and pyroxsulam,

pyrimidinylbenzoates such as bispyribac, bispyribac-sodium,pyribenzoxim, pyriftalid, pyriminobac, pyriminobac-methyl, pyrithiobac,pyrithiobac-sodium,4-[[[2-[(4,6-dimethoxy-2-pyrimidinyl)oxy]phenyl]methyl]amino]-benzoicacid-1-methylethyl ester (CAS 420138-41-6),4-[[[2-[(4,6-dimethoxy-2-pyrimidinyl)oxy]phenyl]methyl]amino]-benzoicacid propyl ester (CAS 420138-40-5),N-(4-bromophenyI)-2-[(4,6-dimethoxy-2-pyrimidinyl)oxy]benzenemethanamine(CAS 420138-01-8) and sulfonylaminocarbonyl-triazolinone herbicides suchas flucarbazone, flucarbazone-sodium, propoxycarbazon,propoxycarbazon-sodium, thiencarbazone and thiencarbazone-methyl. Amongthese, a preferred embodiment of the invention relates to thosecompositions comprising at least one imidazolinone herbicide;

b3) from the group of the photosynthesis inhibitors:

amicarbazone, inhibitors of the photosystem II, e.g. triazineherbicides, including of chlorotriazine, triazinones, triazindiones,methylthiotriazines and pyridazinones such as ametryn, atrazine,chloridazone, cyanazine, desmetryn, dimethametryn,hexazinone,metribuzin, prometon, prometryn, propazin, simazin, simetryn,terbumeton, terbuthylazin, terbutryn and trietazin, aryl urea such aschlorobromuron, chlorotoluron, chloroxuron, dimefuron, diuron,fluometuron, isoproturon, isouron, linuron, metamitron,methabenzthiazuron, metobenzuron, metoxuron, monolinuron, neburon,siduron, tebuthiuron and thiadiazuron, phenyl carbamates such asdesmedipham, karbutilat, phenmedipham, phenmedipham-ethyl, nitrileherbicides such as bromofenoxim, bromoxynil and its salts and esters,ioxynil and its salts and esters, uraciles such as bromacil, lenacil andterbacil, and bentazon and bentazon-sodium, pyridatre, pyridafol,pentanochlor and propanil and inhibitors of the photosystem I such asdiquat, diquat-dibromide, paraquat, paraquat-dichloride andparaquat-dimetilsulfate. Among these, a preferred embodiment of theinvention relates to those compositions comprising at least one arylurea herbicide. Among these, likewise a preferred embodiment of theinvention relates to those compositions comprising at least one triazineherbicide. Among these, likewise a preferred embodiment of the inventionrelates to those compositions comprising at least one nitrile herbicide;

b4) from the group of the protoporphyrinogen-IX oxidase inhibitors:acifluorfen, acifluorfen-sodium, azafenidin, bencarbazone,benzfendizone, bifenox, butafenacil, carfentrazone, carfentrazone-ethyl,chlomethoxyfen, cinidon-ethyl, fluazolate, flufenpyr, flufenpyr-ethyl,flumiclorac, flumiclorac-pentyl, flumioxazin, fluoroglycofen,fluoroglycofen-ethyl, fluthiacet, fluthiacet-methyl, fomesafen,halosafen, lactofen, oxadiargyl, oxadiazon, oxyfluorfen, pentoxazone,profluazol, pyraclonil, pyraflufen, pyraflufen-ethyl, saflufenacil,sulfentrazone, thidiazimin, ethyl[3-[2-chloro-4-fluoro-5-(1-methyl-6-trifluoromethyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-3-yl)phenoxy]-2-pyridyloxy]acetate(CAS 353292-31-6; S-3100),N-ethyl-3-(2,6-dichloro-4-trifluoromethylphenoxy)-5-methyl-1H-pyrazole-1-carboxamide(CAS 452098-92-9),N-tetrahydrofurfuryl-3-(2,6-dichloro-4-trifluoromethylphenoxy)-5-methyl-1H-pyrazole-1-carboxamide(CAS 915396-43-9),N-ethyl-3-(2-chloro-6-fluoro-4-trifluoromethylphenoxy)-5-methyl-1H-pyrazole-1-carboxamide(CAS 452099-05-7),N-tetrahydrofurfuryl-3-(2-chloro-6-fluoro-4-trifluoromethylphenoxy)-5-methyl-1H-pyrazole-1-carboxamide(CAS 45100-03-7) and3-[7-fluoro-3-oxo-4-(prop-2-ynyl)-3,4-dihydro-2H-benzo[1,4]oxazin-6-yl]-1,5-dimethyl-6-thioxo-[1,3,5]triazinan-2,4-dione;

b5) from the group of the bleacher herbicides: PDS inhibitors:beflubutamid, diflufenican, fluridone, flurochloridone, flurtamone,norflurazon, picolinafen, and4-(3-trifluoromethylphenoxy)-2-(4-trifluoromethylphenyl)pyrimidine (CAS180608-33-7), HPPD inhibitors: benzobicyclon, benzofenap, isoxaflutole,mesotrione, pyrasulfotole, pyrazolynate, pyrazoxyfen, sulcotrione,tefuryltrione, tembotrione, topramezone and bicyclopyrone, bleacher,unknown target: aclonifen, amitrole, clomazone and flumeturon; b6) fromthe group of the EPSP synthase inhibitors:

glyphosate, glyphosate-isopropylammonium and glyphosate-trimesium(sulfosate); b7) from the group of the glutamine synthase inhibitors:

bilanaphos (bialaphos), bilanaphos-sodium, glufosinate, glufosinate-Pand glufosinate-ammonium;

b8) from the group of the DHP synthase inhibitors: asulam;

b9) from the group of the mitose inhibitors: compounds of group K1:dinitroanilines such as benfluralin, butralin, dinitramine,ethalfluralin, fluchloralin, oryzalin, pendimethalin, prodiamine andtrifluralin, phosphoramidates such as amiprophos, amiprophos-methyl, andbutamiphos, benzoic acid herbicides such as chlorthal,chlorthal-dimethyl, pyridines such as dithiopyr and thiazopyr,benzamides such as propyzamide and tebutam; compounds of group K2:chlorpropham, propham and carbetamide, among these, compounds of groupK1, in particular dinitroanilines are preferred;

b10) from the group of the VLCFA inhibitors:

chloroacetamides such as acetochlor, alachlor, butachlor, dimethachlor,dimethenamid, dimethenamid-P, metazachlor, metolachlor, metolachlor-S,pethoxamid, pretilachlor, propachlor, propisochlor and thenylchlor,oxyacetanilides such as flufenacet and mefenacet, acetanilides such asdiphenamid, naproanilide and napropamide, tetrazolinones suchfentrazamide, and other herbicides such as anilofos, cafenstrole,fenoxasulfone, ipfencarbazone, piperophos, pyroxasulfone and

isoxazoline compounds of the formula II,

-   -   wherein R⁷, R⁸, R⁹, R¹⁰, W, Z and n have the following meanings:    -   R⁷, R⁸, R⁹, R¹⁰ independently of one another hydrogen, halogen        or C₁-C₄-alkyl;    -   X oxygen or NH;    -   Y phenyl or monocyclic 5-, 6-, 7-, 8-, 9- or 10-membered        heterocyclyl containing, in addition to carbon ring members one,        two or three same or different heteroatoms selected from oxygen,        nitrogen and sulfur as ring members, wherein phenyl and        heterocyclyl are unsubstituted or carry 1, 2 or 3 substituents        R^(yy) selected from halogen, C₁-C₄-alkyl, C₁-C₄-alkoxy,        C₁-C₄-haloalkyl and C₁-C₄-haloalkoxy;        -   preferably phenyl or 5- or 6-membered aromatic heterocyclyl            (hetaryl) which contains, in addition to carbon ring            members, one, two or three nitrogen atoms as ring members,            wherein phenyl and hetaryl are unsubstituted or carry 1, 2            or 3 substituents R^(yy); and    -   n zero or one;

among the isoxazoline compounds of the formula II, preference is givento isoxazoline compounds of the formula II, wherein

-   -   R⁷, R⁸, R⁹, R¹⁰ independently of one another are H, F, Cl or        methyl;    -   X is oxygen;    -   n is 0 or 1; and    -   Y is phenyl, pyrazolyl or 1,2,3-triazolyl, wherein the three        last-mentioned radicals are unsubstituted or carry one, two or        three substituents R^(yy), especially one of the following        radicals

-   -   wherein    -   R¹¹ is halogen, C₁-C₄-alkyl or C₁-C₄-haloalkyl;    -   R¹² is C₁-C₄-alkyl;    -   R¹³ is halogen, C₁-C₄-alkoxy or C₁-C₄-haloalkoxy;    -   R¹⁴ is halogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl or        C₁-C₄-haloalkoxy;    -   m is 0, 1, 2 or 3; and    -   # denotes the point of attachment to the group CR¹³R¹⁴;

among the isoxazoline compounds of the formula II, particular preferenceis given to those isoxazoline compounds of the formula II, wherein

-   -   R⁷ is hydrogen;    -   R⁸ is fluorine;    -   R⁹ is hydrogen or fluorine;    -   R¹⁰ is hydrogen or fluorine;    -   X is oxygen;    -   Y is one of the radicals of the formulae Y¹, Y², Y³ or Y⁴

-   -   -   wherein # denotes the point of attachment to the group            CR⁹R¹⁰;

    -   n is zero or 1, in particular 1; and

among these, especially prefered are the isoxazoline compounds of theformulae II.1, II.2, II.3, II.4, II.5, II.6, II.7, II.8 and II.9

-   -   the isoxazoline compounds of the formula II are known in the        art, e.g. from WO 2006/024820, WO 2006/037945, WO 2007/071900        and WO 2007/096576;    -   among the VLCFA inhibitors, preference is given to        chloroacetamides and oxyacetamides, especially to pyroxasulfone;

b11) from the group of the cellulose biosynthesis inhibitors:chlorthiamid, dichlobenil, flupoxam, isoxaben,1-Cyclohexyl-5-pentafluorphenyloxy-1⁴-[1,2,4,6]thiatriazin-3-ylamine andpiperazine compounds of formula III,

-   -   in which    -   A is phenyl or pyridyl where R^(a) is attached in the        ortho-position to the point of attachment of A to a carbon atom;    -   R^(a) is CN, NO₂, C₁-C₄-alkyl, D-C₃-C₆-cycloalkyl,        C₁-C₄-haloalkyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,        O-D-C₃-C₆-cycloalkyl, S(O)_(q)R^(y), C₂-C₆-alkenyl,        D-C₃-C₆-cycloalkenyl, C₃-C₆-alkenyloxy, C₂-C₆-alkynyl,        C₃-C₆-alkynyloxy, NR^(A)R^(B), tri-C₁-C₄-alkylsilyl,        D-C(═O)—R^(a1), D-P(═O)(R^(a1))₂, phenyl, naphthyl, a 3- to        7-membered monocyclic or 9- or 10-membered bicyclic saturated,        unsaturated or aromatic heterocycle which is attached via carbon        or nitrogen, which contains 1, 2, 3 or 4 heteroatoms selected        from the group consisting of O, N and S, and which may be        partially or fully substituted by groups R^(aa) and/or R^(a1),        and, if R^(a) is attached to a carbon atom, additionally        halogen; R^(y) is C₁-C₆-alkyl, C₃-C₄-alkenyl, C₃-C₄-alkynyl,        NR^(A)R^(B) or C₁-C₄-haloalkyl and q is 0, 1 or 2;    -   R^(A),R^(B) independently of one another are hydrogen,        C₁-C₆-alkyl, C₃-C₆-alkenyl and C₃-C₆-alkynyl; together with the        nitrogen atom to which they are attached, R^(A),R^(B) may also        form a five- or six-membered saturated, partially or fully        unsaturated ring which, in addition to carbon atoms, may contain        1, 2 or 3 heteroatoms selected from the group consisting of O, N        and S, which ring may be substituted by 1 to 3 groups R^(aa);    -   D is a covalent bond, C₁-C₄-alkylene, C₂-C₆-alkenyl or        C₂-C₆-alkynyl;    -   R^(a1) is hydrogen, OH, C₁-C₈-Alkyl, C₁-C₄-haloalkyl,        C₃-C₆-cycloalkyl, C₂-C₈-alkenyl, C₅-C₆-cycloalkenyl,        C₂-C₈-alkynyl, C₁-C₆-alkoxy, C₁-C₄-haloalkoxy, C₃-C₈-alkenyloxy,        C₃-C₈-alkynyloxy, NR^(A)R^(B), C₁-C₆-alkoxyamino,        C₁-C₆-alkylsulfonylamino, C₁-C₆-alkylaminosulfonylamino,        [di-(C₁-C₆)alkylamino]sulfonylamino, C₃-C₆-alkenylamino,        C₃-C₆-alkynylamino, N—(C₂-C₆-alkenyl)-N—(C₁-C₆-alkyl)amino,        N—(C₂-C₆-alkynyl)-N—(C₁-C₆-alkyl)amino,        N—(C₁-C₆-alkoxy)-N—(C₁-C₆-alkyl)amino,        N—(C₂-C₆-alkenyl)-N—(C₁-C₆-alkoxy)amino,        N—(C₂-C₆-alkynyl)-N—(C₁-C₆-alkoxy)-amino, C₁-C₆-alkylsulfonyl,        tri-C₁-C₄-alkylsilyl, phenyl, phenoxy, phenylamino or a 5- or        6-membered monocyclic or 9- or 10-membered bicyclic heterocycle        which contains 1, 2, 3 or 4 heteroatoms selected from the group        consisting of O, N and S, where the cyclic groups are        unsubstituted or substituted by 1, 2, 3 or 4 groups R^(aa);    -   R^(aa) is halogen, OH, CN, NO₂, C₁-C₄-alkyl, C₁-C₄-haloalkyl,        C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, S(O)_(q)R^(y), D-C(═O)—R^(a1)        and tri-C₁-C₄-alkylsilyl;

R^(b) independently of one another are hydrogen, CN, NO₂, halogen,C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₂-C₄-alkenyl, C₃-C₆-alkynyl,C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, benzyl or S(O)_(q)R^(y),

-   -   R^(b) together with the group R^(a) or R^(b) attached to the        adjacent ring atom may also form a five- or six-membered        saturated or partially or fully unsaturated ring which, in        addition to carbon atoms, may contain 1, 2 or 3 heteroatoms        selected from the group consisting of O, N and S, which ring may        be partially or fully substituted by R^(aa);    -   p is 0, 1, 2 or 3;    -   R¹⁵ is hydrogen, OH, CN, C₁-C₁₂-alkyl, C₃-C₁₂-alkenyl,        C₃-C₁₂-alkynyl, C₁-C₄-alkoxy, C₃-C₆-cycloalkyl,        C₅-C₆-cycloalkenyl, NR^(A)R^(B), S(O)_(n)R^(Y),        S(O)_(n)NR^(A)R^(B), C(═O)R²⁵, CONR^(A)R^(B), phenyl or a 5- or        6-membered monocyclic or 9- or 10-membered bicyclic aromatic        heterocycle which contains 1, 2, 3 or 4 heteroatoms selected        from the group consisting of O, N and S, where the cyclic groups        are attached via D¹ and are unsubstituted or substituted by 1,        2, 3 or 4 groups R^(aa), and also the following partially or        fully R^(aa)-substituted groups: C₁-C₄-alkyl, C₃-C₄-alkenyl,        C₃-C₄-alkynyl, C₁-C₄-alkoxy, C₃-C₆-cycloalkyl,        C₅-C₆-cycloalkenyl, NR^(A)R^(B), S(O)_(n)R^(y),        S(O)_(n)NR^(A)R^(B), C(═O)R²⁵, CONR^(A)R^(B);        -   preferably is hydrogen, OH, CN, C₁-C₁₂-alkyl,            C₃-C₁₂-alkenyl, C₃-C₁₂-alkynyl, C₁-C₄-alkoxy,            C₃-C₆-cycloalkyl, C₅-C₆-cycloalkenyl, NR^(A)R^(B),            S(O)_(n)R^(y), S(O)_(n)NR^(A)R^(B), C(═O)R²⁵, CONR^(A)R^(B),            phenyl or a 5- or 6-membered monocyclic or 9- or 10-membered            bicyclic aromatic heterocycle which contains 1, 2, 3 or 4            heteroatoms selected from the group consisting of O, N and            S, where the cyclic groups are attached via D¹ and are            unsubstituted or substituted by 1, 2, 3 or 4 groups R^(aa),            and also the following partially or fully R^(aa)-substituted            groups: C₁-C₄-alkyl, C₃-C₄-alkenyl and C₃-C₄-alkynyl;        -   R²⁵ is hydrogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₁-C₄-alkoxy            or C₁-C₄-haloalkoxy;        -   D¹ is carbonyl or a group D;        -   where in groups R¹⁵, R^(a) and their sub-substituents the            carbon chains and/or the cyclic groups may carry 1, 2, 3 or            4 substituents R^(aa) and/or R^(a1);    -   R¹⁶ is C₁-C₄-alkyl, C₃-C₄-alkenyl or C₃-C₄-alkynyl;    -   R¹⁷ is OH, NH₂, C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₃-C₆-alkenyl,        C₃-C₆-alkynyl, C₁-C₄-hydroxyalkyl, C₁-C₄-cyanoalkyl,        C₁-C₄-haloalkyl, C₁-C₄-alkoxy-C₁-C₄-alkyl or C(═O)R²⁵;    -   R¹⁸ is hydrogen, halogen, C₁-C₄-alkyl or C₁-C₄-haloalkyl, or R¹⁸        and R¹⁹ together are a covalent bond;    -   R¹⁹, R²⁰, R²¹, R²¹ independently of one another are hydrogen,        halogen, OH, CN, NO₂, C₁-C₄-alkyl, C₁-C₄-haloalkyl,        C₂-C₆-alkenyl, C₂-C₆-alkynyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,        C₃-C₆-cycloalkyl, C₃-C₆-cycloalkenyl and C₃-C₆-cycloalkynyl;    -   R²³, R²⁴ independently of one another are hydrogen, halogen, OH,        haloalkyl, NR^(A)R^(B), NR^(A)C(O)R²⁶, CN, NO₂, C₁-C₄-alkyl,        C₁-C₄-haloalkyl, C₂-C₄-alkenyl, C₃-C₆-alkynyl, C₁-C₄-alkoxy,        C₁-C₄-haloalkoxy, O—C(O)R²⁶, phenoxy or benzyloxy, where in        groups R²³ and R²⁴ the carbon chains and/or the cyclic groups        may carry 1, 2, 3 or 4 substituents R^(aa);    -   R²⁶ is C₁-C₄-alkyl or NR^(A)R^(B);    -   among the isoxazoline compounds of the piperazin compounds of        formula III, preference is given to the piperazine compounds of        the formula III, wherein    -   A is phenyl or pyridyl where Ra is attached in the        ortho-position to the point of attachment of A to a carbon atom;    -   R^(a) is CN, NO₂, C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₁-C₄-alkoxy,        C₁-C₄-haloalkoxy or D-C(═O)—R^(a1);        -   R^(y) is C₁-C₆-alkyl, C₃-C₄-alkenyl, C₃-C₄-alkynyl,            NR^(A)R^(B) or C₁-C₄-haloalkyl and q is 0, 1 or 2;        -   R^(A),R^(B) independently of one another are hydrogen,            C₁-C₆-alkyl, C₃-C₆-alkenyl and C₃-C₆-alkynyl; together with            the nitrogen atom to which they are attached, R^(A),R^(B)            may also form a five- or six-membered saturated, partially            or fully unsaturated ring which, in addition to carbon            atoms, may contain 1, 2 or 3 heteroatoms selected from the            group consisting of O, N and S, which ring may be            substituted by 1 to 3 groups R^(aa);        -   D is a covalent bond or C₁-C₄-alkylene;        -   R^(a1) is hydrogen, OH, C₁-C₈-Alkyl, C₁-C₄-haloalkyl,            C₃-C₆-cycloalkyl;        -   R^(aa) is halogen, OH, CN, NO₂, C₁-C₄-alkyl,            C₁-C₄-haloalkyl, C₁-C₄-alkoxy, C₁-C₄-haloalkoxy,            S(O)_(q)R^(y), D-C(═O)—R^(a1) and tri-C₁-C₄-alkylsilyl;    -   R^(b) independently of one another is CN, NO₂, halogen,        C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₂-C₄-alkenyl, C₃-C₆-alkynyl,        C₁-C₄-alkoxy, C₁-C₄-haloalkoxy, benzyl or S(O)_(q)R^(y), R^(b)        together with the group R^(a) or R^(b) attached to the adjacent        ring atom may also form a five- or six-membered saturated or        partially or fully unsaturated ring which, in addition to carbon        atoms, may contain 1, 2 or 3 heteroatoms selected from the group        consisting of O, N and S, which ring may be partially or fully        substituted by R^(aa);    -   p is 0 or 1;    -   R¹⁵ is hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-alkenyl, C₃-C₁₂-alkynyl,        C₁-C₄-alkoxy or C(═O)R²⁵, which can be partially or fully        substituted by R^(aa)-groups;    -   preferably is hydrogen, C₁-C₁₂-alkyl, C₃-C₁₂-alkenyl,        C₃-C₁₂-alkynyl, C₁-C₄-alkoxy or C(═O)R²⁵;        -   R²⁵ is hydrogen, C₁-C₄-alkyl, C₁-C₄-haloalkyl, C₁-C₄-alkoxy            or C₁-C₄-haloalkoxy; where in groups R¹⁵, R^(a) and their            sub-substituents the carbon chains and/or the cyclic groups            may carry 1, 2, 3 or 4 substituents R^(aa) and/or R^(a1);    -   R¹⁶ is C₁-C₄-alkyl;    -   R¹⁷ is OH, NH₂, C₁-C₄-alkyl, C₃-C₆-cycloalkyl, C₁-C₄-haloalkyl        or C(═O)R²⁵;    -   R¹⁸ is hydrogen, or R¹⁸ and R¹⁹ together are a covalent bond;    -   R¹⁹, R²⁰, R²¹, R²¹ independently of one another are hydrogen;    -   R²³, R²⁴ independently of one another are hydrogen, halogen or        OH;

b12) from the group of the decoupler herbicides:

dinoseb, dinoterb and DNOC and its salts;

b13) from the group of the auxin herbicides:

2,4-D and its salts and esters, 2,4-DB and its salts and esters,aminopyralid and its salts such asaminopyralid-tris(2-hydroxypropyl)ammonium and its esters, benazolin,benazolin-ethyl, chloramben and its salts and esters, clomeprop,clopyralid and its salts and esters, dicamba and its salts and esters,dichlorprop and its salts and esters, dichlorprop-P and its salts andesters, fluroxypyr, fluroxypyr-butometyl, fluroxypyr-meptyl, MCPA andits salts and esters, MCPA-thioethyl, MCPB and its salts and esters,mecoprop and its salts and esters, mecoprop-P and its salts and esters,picloram and its salts and esters, quinclorac, quinmerac, TBA (2,3,6)and its salts and esters, triclopyr and its salts and esters, andaminocyclopyrachlor and its salts and esters;

b14) from the group of the auxin transport inhibitors: diflufenzopyr,diflufenzopyr-sodium, naptalam and naptalam-sodium;

b15) from the group of the other herbicides: bromobutide, chlorflurenol,chlorflurenol-methyl, cinmethylin, cumyluron, dalapon, dazomet,difenzoquat, difenzoquat-metilsulfate, dimethipin, DSMA, dymron,endothal and its salts, etobenzanid, flamprop, flamprop-isopropyl,flamprop-methyl, flamprop-M-isopropyl, flamprop-M-methyl, flurenol,flurenol-butyl, flurprimidol, fosamine, fosamine-ammonium, indanofan,indaziflam, maleic hydrazide, mefluidide, metam, methyl azide, methylbromide, methyl-dymron, methyl iodide, MSMA, oleic acid, oxaziclomefone,pelargonic acid, pyributicarb, quinoclamine, triaziflam, tridiphane and6-chloro-3-(2-cyclopropyl-6-methylphenoxy)-4-pyridazinol (CAS499223-49-3) and its salts and esters.

Moreover, it may be useful to apply the benzoxazinones of the formula Iin combination with safeners. Safeners are chemical compounds whichprevent or reduce damage on useful plants without having a major impacton the herbicidal action of the benzoxazinones of the formula I towardsunwanted plants. They can be applied either before sowings (e.g. on seedtreatments, shoots or seedlings) or in the pre-emergence application orpost-emergence application of the useful plant.

Furthermore, the safeners C, the benzoxazinones I and/or the herbicidesB can be applied simultaneously or in succession.

Suitable safeners are e.g. (quinolin-8-oxy)acetic acids,1-phenyl-5-haloalkyl-1H-1,2,4-triazol-3-carboxylic acids,1-phenyl-4,5-dihydro-5-alkyl-1H-pyrazol-3,5-dicarboxylic acids,4,5-dihydro-5,5-diaryl-3-isoxazol carboxylic acids, dichloroacetamides,alpha-oximinophenylacetonitriles, acetophenonoximes,4,6-dihalo-2-phenylpyrimidines,N-[[4-(aminocarbonyl)phenyl]sulfonyl]-2-benzoic amides, 1,8-naphthalicanhydride, 2-halo-4-(haloalkyl)-5-thiazol carboxylic acids,phosphorthiolates and N-alkyl-O-phenylcarbamates and theiragriculturally acceptable salts and their agriculturally acceptablederivatives such amides, esters, and thioesters, provided they have anacid group.

Examples of preferred safeners C are benoxacor, cloquintocet,cyometrinil, cyprosulfamide, dichlormid, dicyclonon, dietholate,fenchlorazole, fenclorim, flurazole, fluxofenim, furilazole, isoxadifen,mefenpyr, mephenate, naphthalic anhydride, oxabetrinil,4-(dichloroacetyl)-1-oxa-4-azaspiro[4.5]decane (MON4660, CAS 71526-07-3)and 2,2,5-trimethyl-3-(dichloroacetyl)-1,3-oxazolidine (R-29148, CAS52836-31-4), andN-(2-Methoxybenzoyl)-4-[(methylaminocarbonyl)amino]benzenesulfonamide(CAS 129531-12-0).

Especially preferred safeners C are benoxacor, cloquintocet,cyprosulfamide, dichlormid, fenchlorazole, fenclorim, flurazole,fluxofenim, furilazole, isoxadifen, mefenpyr, naphthalic anhydride,oxabetrinil, 4-(dichloroacetyl)-1-oxa-4-azaspiro[4.5]decane (MON4660,CAS 71526-07-3) and 2,2,5-trimethyl-3-(dichloroacetyl)-1,3-oxazolidine(R-29148, CAS 52836-31-4), andN-(2-Methoxybenzoyl)-4-[(methylaminocarbonyl)amino]benzenesulfonamide(CAS 129531-12-0).

Particularly preferred safeners C are benoxacor, cloquintocet,cyprosulfamide, dichlormid, fenchlorazole, fenclorim, furilazole,isoxadifen, mefenpyr, 4-(dichloroacetyl)-1-oxa-4-azaspiro-[4.5]decane(MON4660, CAS 71526-07-3) and2,2,5-trimethyl-3-(dichloroacetyl)-1,3-oxazolidine (R-29148, CAS52836-31-4), andN-(2-Methoxybenzoyl)-4-[(methylaminocarbonyl)amino]benzenesulfonamide(CAS 129531-12-0).

Particularly preferred safeners C, which, as component C, areconstituent of the composition according to the invention are thesafeners C as defined above; in particular the safeners C.1-C.13 listedbelow in table C:

TABLE C Safener C C.1 benoxacor C.2 cloquintocet C.3 cyprosulfamide C.4dichlormid C.5 fenchlorazole C.6 fenclorim C.7 furilazole C.8 isoxadifenC.9 mefenpyr C.10 naphtalic acid anhydride C.114-(dichloroacetyl)-1-oxa-4-azaspiro[4.5]decane (MON4660, CAS 71526-07-3)C.12 2,2,5-trimethyl-3-(dichloro-acetyl)-1,3-oxazolidine (R-29148, CAS52836-31-4) C.13 N-(2-Methoxybenzoyl)-4-[(methylaminocarbonyl)amino]benzenesulfonamide (CAS 129531-12-0)

The active compounds B of groups b1) to b15) and the active compounds Care known herbicides and safeners, see, for example, The Compendium ofPesticide Common Names (www.alanwood.net/pesticides/); Farm ChemicalsHandbook 2000 volume 86, Meister Publishing Company, 2000; B. Hock, C.Fedtke, R. R. Schmidt, Herbizide [Herbicides], Georg Thieme Verlag,Stuttgart 1995; W. H. Ahrens, Herbicide Handbook, 7th edition, WeedScience Society of America, 1994; and K. K. Hatzios, Herbicide Handbook,Supplement for the 7th edition, Weed Science Society of America, 1998.2,2,5-Trimethyl-3-(dichloroacetyl)-1,3-oxazolidine [CAS No. 52836-31-4]is also referred to as R-29148.4-(Dichloroacetyl)-1-oxa-4-azaspiro[4.5]decane [CAS No. 71526-07-3] isalso referred to as AD-67 and MON 4660. Further herbicidally activecompounds are known from WO 96/26202, WO 97/41116, WO 97/41117, WO97/41118 and WO 01/83459 and also from W. Kramer et al. (ed.) “ModernCrop Protection Compounds”, Vol. 1, Wiley VCH, 2007 and the literaturecited therein.

It is generally preferred to use the compounds of the invention incombination with herbicides that are selective for the crop beingtreated and which complement the spectrum of weeds controlled by thesecompounds at the application rate employed. It is further generallypreferred to apply the compounds of the invention and othercomplementary herbicides at the same time, either as a combinationformulation or as a tank mix.

It is recognized that the polynucleotide molecules and polypeptides ofthe invention encompass polynucleotide molecules and polypeptidescomprising a nucleotide or an amino acid sequence that is sufficientlyidentical to nucleotide sequences set forth in SEQ ID Nos: 1, 3, 5, 7,9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43,or 45, or to the amino acid sequences set forth in SEQ ID Nos: 2, 4, 6,8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42,44, or 46. The term “sufficiently identical” is used herein to refer toa first amino acid or nucleotide sequence that contains a sufficient orminimum number of identical or equivalent (e.g., with a similar sidechain) amino acid residues or nucleotides to a second amino acid ornucleotide sequence such that the first and second amino acid ornucleotide sequences have a common structural domain and/or commonfunctional activity.

Generally, “sequence identity” refers to the extent to which twooptimally aligned DNA or amino acid sequences are invariant throughout awindow of alignment of components, e.g., nucleotides or amino acids. An“identity fraction” for aligned segments of a test sequence and areference sequence is the number of identical components that are sharedby the two aligned sequences divided by the total number of componentsin reference sequence segment, i.e., the entire reference sequence or asmaller defined part of the reference sequence. “Percent identity” isthe identity fraction times 100. Optimal alignment of sequences foraligning a comparison window are well known to those skilled in the artand may be conducted by tools such as the local homology algorithm ofSmith and Waterman, the homology alignment algorithm of Needleman andWunsch, the search for similarity method of Pearson and Lipman, andpreferably by computerized implementations of these algorithms such asGAP, BESTFIT, FASTA, and TFASTA available as part of the GCG. WisconsinPackage. (Accelrys Inc. Burlington, Mass.)

Polynucleotides and Oligonucleotides

By an “isolated polynucleotide”, including DNA, RNA, or a combination ofthese, single or double stranded, in the sense or antisense orientationor a combination of both, dsRNA or otherwise, we mean a polynucleotidewhich is at least partially separated from the polynucleotide sequenceswith which it is associated or linked in its native state. Preferably,the isolated polynucleotide is at least 60% free, preferably at least75% free, and most preferably at least 90% free from other componentswith which they are naturally associated. As the skilled addressee wouldbe aware, an isolated polynucleotide can be an exogenous polynucleotidepresent in, for example, a transgenic organism which does not naturallycomprise the polynucleotide. Furthermore, the terms “polynucleotide(s)”,“nucleic acid sequence(s)”, “nucleotide sequence(s)”, “nucleic acid(s)”,“nucleic acid molecule” are used interchangeably herein and refer tonucleotides, either ribonucleotides or deoxyribonucleotides or acombination of both, in a polymeric unbranched form of any length.

The term “mut-PPO nucleic acid” refers to a PPO nucleic acid having asequence that is mutated from a wild-type PPO nucleic acid and thatconfers increased benzoxazinone-derivative herbicide tolerance to aplant in which it is expressed. Furthermore, the term “mutatedprotoporphyrinogen oxidase (mut-PPO)” refers to the replacement of anamino acid of the wild-type primary sequences SEQ ID NO: 2, 4, 6, 8, 10,12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, or46, or a variant, a derivative, a homologue, an orthologue, or paraloguethereof, with another amino acid. The expression “mutated amino acid”will be used below to designate the amino acid which is replaced byanother amino acid, thereby designating the site of the mutation in theprimary sequence of the protein.

In a preferred embodiment, the PPO nucleotide sequence comprises thesequence of SEQ ID NO: 1, 25, 37 or 39 or a variant or derivativethereof.

Furthermore, it will be understood by the person skilled in the art thatthe PPO nucleotide sequences encompasse homologues, paralogues and andorthologues of SEQ ID NO: 1, 25, 37 or 39 as defined hereinafter.

The term “variant” with respect to a sequence (e.g., a polypeptide ornucleic acid sequence such as—for example—a transcription regulatingnucleotide sequence of the invention) is intended to mean substantiallysimilar sequences. For nucleotide sequences comprising an open readingframe, variants include those sequences that, because of the degeneracyof the genetic code, encode the identical amino acid sequence of thenative protein. Naturally occurring allelic variants such as these canbe identified with the use of well-known molecular biology techniques,as, for example, with polymerase chain reaction (PCR) and hybridizationtechniques. Variant nucleotide sequences also include syntheticallyderived nucleotide sequences, such as those generated, for example, byusing site-directed mutagenesis and for open reading frames, encode thenative protein, as well as those that encode a polypeptide having aminoacid substitutions relative to the native protein. Generally, nucleotidesequence variants of the invention will have at least 30, 40, 50, 60, to70%, e.g., preferably 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, to 79%,generally at least 80%, e.g., 81%-84%, at least 85%, e.g., 86%, 87%,88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, to 98% and 99%nucleotide “sequence identity” to the nucleotide sequence of SEQ ID NO:SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31,33, 35, 37, 39, 41, 43, or 45. The % identity of a polynucleotide isdetermined by GAP (Needleman and Wunsch, 1970) analysis (GCG program)with a gap creation penalty=5, and a gap extension penalty=0.3. Unlessstated otherwise, the query sequence is at least 45 nucleotides inlength, and the GAP analysis aligns the two sequences over a region ofat least 45 nucleotides. Preferably, the query sequence is at least 150nucleotides in length, and the GAP analysis aligns the two sequencesover a region of at least 150 nucleotides. More preferably, the querysequence is at least 300 nucleotides in length and the GAP analysisaligns the two sequences over a region of at least 300 nucleotides. Evenmore preferably, the GAP analysis aligns the two sequences over theirentire length.

Polypeptides

By “substantially purified polypeptide” or “purified” a polypeptide ismeant that has been separated from one or more lipids, nucleic acids,other polypeptides, or other contaminating molecules with which it isassociated in its native state. It is preferred that the substantiallypurified polypeptide is at least 60% free, more preferably at least 75%free, and more preferably at least 90% free from other components withwhich it is naturally associated. As the skilled addressee willappreciate, the purified polypeptide can be a recombinantly producedpolypeptide. The terms “polypeptide” and “protein” are generally usedinterchangeably and refer to a single polypeptide chain which may or maynot be modified by addition of non-amino acid groups. It would beunderstood that such polypeptide chains may associate with otherpolypeptides or proteins or other molecules such as co-factors. Theterms “proteins” and “polypeptides” as used herein also includevariants, mutants, modifications, analogous and/or derivatives of thepolypeptides of the invention as described herein.

The % identity of a polypeptide is determined by GAP (Needleman andWunsch, 1970) analysis (GCG program) with a gap creation penalty=5, anda gap extension penalty=0.3. The query sequence is at least 25 aminoacids in length, and the GAP analysis aligns the two sequences over aregion of at least 25 amino acids. More preferably, the query sequenceis at least 50 amino acids in length, and the GAP analysis aligns thetwo sequences over a region of at least 50 amino acids. More preferably,the query sequence is at least 100 amino acids in length and the GAPanalysis aligns the two sequences over a region of at least 100 aminoacids. Even more preferably, the query sequence is at least 250 aminoacids in length and the GAP analysis aligns the two sequences over aregion of at least 250 amino acids. Even more preferably, the GAPanalysis aligns the two sequences over their entire length.

With regard to a defined polypeptide, it will be appreciated that %identity figures higher than those provided above will encompasspreferred embodiments. Thus, where applicable, in light of the minimum %identity figures, it is preferred that the PPO polypeptide of theinvention comprises an amino acid sequence which is at least 40%, morepreferably at least 45%, more preferably at least 50%, more preferablyat least 55%, more preferably at least 60%, more preferably at least65%, more preferably at least 70%, more preferably at least 75%, morepreferably at least 80%, more preferably at least 85%, more preferablyat least 90%, more preferably at least 91%, more preferably at least92%, more preferably at least 93%, more preferably at least 94%, morepreferably at least 95%, more preferably at least 96%, more preferablyat least 97%, more preferably at least 98%, more preferably at least99%, more preferably at least 99.1%, more preferably at least 99.2%,more preferably at least 99.3%, more preferably at least 99.4%, morepreferably at least 99.5%, more preferably at least 99.6%, morepreferably at least 99.7%, more preferably at least 99.8%, and even morepreferably at least 99.9% identical to SEQ ID NO: 2, 4, 6, 8, 10, 12,14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, or 46.

By “variant” polypeptide is intended a polypeptide derived from theprotein of SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26,28, 30, 32, 34, 36, 38, 40, 42, 44, or 46 by deletion (so-calledtruncation) or addition of one or more amino acids to the N-terminaland/or C-terminal end of the native protein; deletion or addition of oneor more amino acids at one or more sites in the native protein; orsubstitution of one or more amino acids at one or more sites in thenative protein. Such variants may result from, for example, geneticpolymorphism or from human manipulation. Methods for such manipulationsare generally known in the art.

“Derivatives” of a protein encompass peptides, oligopeptides,polypeptides, proteins and enzymes having amino acid substitutions,deletions and/or insertions relative to the unmodified protein inquestion and having similar biological and functional activity as theunmodified protein from which they are derived.

“Homologues” of a protein encompass peptides, oligopeptides,polypeptides, proteins and enzymes having amino acid substitutions,deletions and/or insertions relative to the unmodified protein inquestion and having similar biological and functional activity as theunmodified protein from which they are derived.

A deletion refers to removal of one or more amino acids from a protein.

An insertion refers to one or more amino acid residues being introducedinto a predetermined site in a protein. Insertions may compriseN-terminal and/or C-terminal fusions as well as intra-sequenceinsertions of single or multiple amino acids. Generally, insertionswithin the amino acid sequence will be smaller than N- or C-terminalfusions, of the order of about 1 to 10 residues. Examples of N- orC-terminal fusion proteins or peptides include the binding domain oractivation domain of a transcriptional activator as used in the yeasttwo-hybrid system, phage coat proteins, (histidine)-6-tag, glutathioneS-transferase-tag, protein A, maltose-binding protein, dihydrofolatereductase, Tag·100 epitope, c-myc epitope, FLAG®-epitope, lacZ, CMP(calmodulin-binding peptide), HA epitope, protein C epitope and VSVepitope.

A substitution refers to replacement of amino acids of the protein withother amino acids having similar properties (such as similarhydrophobicity, hydrophilicity, antigenicity, propensity to form orbreak a-helical structures or β-sheet structures). Amino acidsubstitutions are typically of single residues, but may be clustereddepending upon functional constraints placed upon the polypeptide andmay range from 1 to 10 amino acids; insertions will usually be of theorder of about 1 to 10 amino acid residues. The amino acid substitutionsare preferably conservative amino acid substitutions. Conservativesubstitution tables are well known in the art (see for example Creighton(1984) Proteins. W.H. Freeman and Company (Eds).

TABLE 2 Examples of conserved amino acid substitutions ConservativeConservative Residue Substitutions Residue Substitutions Ala Ser LeuIle; Val Arg Lys Lys Arg; Gln Asn Gln; His Met Leu; Ile Asp Glu Phe Met;Leu; Tyr Gln Asn Ser Thr; Gly Cys Ser Thr Ser; Val Glu Asp Trp Tyr GlyPro Tyr Trp; Phe His Asn; Gln Val Ile; Leu Ile Leu, Val

Amino acid substitutions, deletions and/or insertions may readily bemade using peptide synthetic techniques well known in the art, such assolid phase peptide synthesis and the like, or by recombinant DNAmanipulation. Methods for the manipulation of DNA sequences to producesubstitution, insertion or deletion variants of a protein are well knownin the art. For example, techniques for making substitution mutations atpredetermined sites in DNA are well known to those skilled in the artand include M13 mutagenesis, T7-Gen in vitro mutagenesis (USB,Cleveland, Ohio), QuickChange Site Directed mutagenesis (Stratagene, SanDiego, Calif.), PCR-mediated site-directed mutagenesis or othersite-directed mutagenesis protocols.

“Derivatives” further include peptides, oligopeptides, polypeptideswhich may, compared to the amino acid sequence of thenaturally-occurring form of the protein, such as the protein ofinterest, comprise substitutions of amino acids with non-naturallyoccurring amino acid residues, or additions of non-naturally occurringamino acid residues. “Derivatives” of a protein also encompass peptides,oligopeptides, polypeptides which comprise naturally occurring altered(glycosylated, acylated, prenylated, phosphorylated, myristoylated,sulphated etc.) or non-naturally altered amino acid residues compared tothe amino acid sequence of a naturally-occurring form of thepolypeptide. A derivative may also comprise one or more non-amino acidsubstituents or additions compared to the amino acid sequence from whichit is derived, for example a reporter molecule or other ligand,covalently or non-covalently bound to the amino acid sequence, such as areporter molecule which is bound to facilitate its detection, andnon-naturally occurring amino acid residues relative to the amino acidsequence of a naturally-occurring protein. Furthermore, “derivatives”also include fusions of the naturally-occurring form of the protein withtagging peptides such as FLAG, HIS6 or thioredoxin (for a review oftagging peptides, see Terpe, Appl. Microbiol. Biotechnol. 60, 523-533,2003).

“Orthologues” and “paralogues” encompass evolutionary concepts used todescribe the ancestral relationships of genes. Paralogues are geneswithin the same species that have originated through duplication of anancestral gene; orthologues are genes from different organisms that haveoriginated through speciation, and are also derived from a commonancestral gene. A non-limiting list of examples of such orthologues areshown in Table 1.

It is well-known in the art that paralogues and orthologues may sharedistinct domains harboring suitable amino acid residues at given sites,such as binding pockets for particular substrates or binding motifs forinteraction with other proteins.

The term “domain” refers to a set of amino acids conserved at specificpositions along an alignment of sequences of evolutionarily relatedproteins. While amino acids at other positions can vary betweenhomologues, amino acids that are highly conserved at specific positionsindicate amino acids that are likely essential in the structure,stability or function of a protein. Identified by their high degree ofconservation in aligned sequences of a family of protein homologues,they can be used as identifiers to determine if any polypeptide inquestion belongs to a previously identified polypeptide family.

The term “motif” or “consensus sequence” refers to a short conservedregion in the sequence of evolutionarily related proteins. Motifs arefrequently highly conserved parts of domains, but may also include onlypart of the domain, or be located outside of conserved domain (if all ofthe amino acids of the motif fall outside of a defined domain).

Specialist databases exist for the identification of domains, forexample, SMART (Schultz et al. (1998) Proc. Natl. Acad. Sci. USA 95,5857-5864; Letunic et al. (2002) Nucleic Acids Res 30, 242-244),InterPro (Mulder et al., (2003) Nucl. Acids. Res. 31, 315-318), Prosite(Bucher and Bairoch (1994), A generalized profile syntax forbiomolecular sequences motifs and its function in automatic sequenceinterpretation. (In) ISMB-94; Proceedings 2nd International Conferenceon Intelligent Systems for Molecular Biology. Altman R., Brutlag D.,Karp P., Lathrop R., Searls D., Eds., pp53-61, AAAI Press, Menlo Park;Hulo et al., Nucl. Acids. Res. 32:D134-D137, (2004)), or Pfam (Batemanet al., Nucleic Acids Research 30(1): 276-280 (2002)). A set of toolsfor in silico analysis of protein sequences is available on the ExPASyproteomics server (Swiss Institute of Bioinformatics (Gasteiger et al.,ExPASy: the proteomics server for in-depth protein knowledge andanalysis, Nucleic Acids Res. 31:3784-3788(2003)). Domains or motifs mayalso be identified using routine techniques, such as by sequencealignment.

Methods for the alignment of sequences for comparison are well known inthe art, such methods include GAP, BESTFIT, BLAST, FASTA and TFASTA. GAPuses the algorithm of Needleman and Wunsch ((1970) J Mol Biol 48:443-453) to find the global (i.e. spanning the complete sequences)alignment of two sequences that maximizes the number of matches andminimizes the number of gaps. The BLAST algorithm (Altschul et al.(1990) J Mol Biol 215: 403-10) calculates percent sequence identity andperforms a statistical analysis of the similarity between the twosequences. The software for performing BLAST analysis is publiclyavailable through the National Centre for Biotechnology Information(NCBI). Homologues may readily be identified using, for example, theClustalW multiple sequence alignment algorithm (version 1.83), with thedefault pairwise alignment parameters, and a scoring method inpercentage. Global percentages of similarity and identity may also bedetermined using one of the methods available in the MatGAT softwarepackage (Campanella et al., BMC Bioinformatics. 2003 Jul. 10; 4:29.MatGAT: an application that generates similarity/identity matrices usingprotein or DNA sequences.). Minor manual editing may be performed tooptimise alignment between conserved motifs, as would be apparent to aperson skilled in the art. Furthermore, instead of using full-lengthsequences for the identification of homologues, specific domains mayalso be used. The sequence identity values may be determined over theentire nucleic acid or amino acid sequence or over selected domains orconserved motif(s), using the programs mentioned above using the defaultparameters. For local alignments, the Smith-Waterman algorithm isparticularly useful (Smith T F, Waterman M S (1981) J. Mol. Biol 147(1);195-7).

The inventors of the present invention have found that by substitutingone or more of the key amino acid residues the herbicide tolerance orresistance could be remarkably increased as compared to the activity ofthe wild type PPO enzymes with SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16,18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, or 46. Preferredsubstitutions of mut-PPO are those that increase the herbicide toleranceof the plant, but leave the biological activitiy of the oxidase activitysubstantially unaffected.

Accordingly, in another object of the present invention the key aminoacid residues of a PPO enzyme, a variant, derivative, orthologue,paralogue or homologue thereof, is substituted by any other amino acid.

In a preferred embodiment, the key amino acid residues of a PPO enzyme,a variant, derivative, orthologue, paralogue or homologue thereof, issubstituted by a conserved amino acid as depicted in Table 2.

It will be understood by the person skilled in the art that amino acidslocated in a close proximity to the positions of amino acids mentionedbelow may also be substituted. Thus, in another embodiment the variantof SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30,32, 34, 36, 38, 40, 42, 44, or 46, a variant, derivative, orthologue,paralogue or homologue thereof comprises a mut-PPO, wherein an aminoacid ±3, ±2 or ±1 amino acid positions from a key amino acid issubstituted by any other amino acid.

Based on techniques well-known in the art, a highly characteristicsequence pattern can be developed, by means of which further of mut-PPOcandidates with the desired activity may be searched.

Searching for further mut-PPO candidates by applying a suitable sequencepattern would also be encompassed by the present invention. It will beunderstood by a skilled reader that the present sequence pattern is notlimited by the exact distances between two adjacent amino acid residuesof said pattern. Each of the distances between two neighbours in theabove patterns may, for example, vary independently of each other by upto ±10, ±5, ±3, ±2 or ±1 amino acid positions without substantiallyaffecting the desired activity.

Furthermore, by applying the method of site directed mutagenesis, theinventors of the present invention have identified specific combinationsof mutations, which combination refers to a substitution of thePhenylalanine residue at position 420 in SEQ ID NO:2 or 4, combined witha second substitution of the Leucin at position 397 in SEQ ID NO:2 or 4.

Thus, in a particularly preferred embodiment, the variant or derivativeof the mut-PPO of SEQ ID NO: 2 or SEQ ID NO: 4 is selected from thecombined amino acid substitutions of the following Table 3a.

TABLE 3a SEQ ID NO: 2 or SEQ ID NO: 4 (combined amino acid substitutionsobtained by site directed mutagenesis.) Key amino Combination SEQ acidposition Preferred Number ID NO: combination Substitution 1 2 or 4Leu397 Gly Phe420 Met 2 2 or 4 Leu397 Ala Phe420 Met 3 2 or 4 Leu397 SerPhe420 Met 4 2 or 4 Leu397 Thr Phe420 Met 5 2 or 4 Leu397 Cys Phe420 Met6 2 or 4 Leu397 Val Phe420 Met 7 2 or 4 Leu397 Ile Phe420 Met 8 2 or 4Leu397 Met Phe420 Met 9 2 or 4 Leu397 Pro Phe420 Met 10 2 or 4 Leu397Phe Phe420 Met 11 2 or 4 Leu397 Tyr Phe420 Met 12 2 or 4 Leu397 TrpPhe420 Met 13 2 or 4 Leu397 Asp Phe420 Met 14 2 or 4 Leu397 Glu Phe420Met 15 2 or 4 Leu397 Asn Phe420 Met 16 2 or 4 Leu397 Gln Phe420 Met 17 2or 4 Leu397 His Phe420 Met 18 2 or 4 Leu397 Lys Phe420 Met 19 2 or 4Leu397 Arg Phe420 Met 20 2 or 4 Leu397 Gly Phe420 Val 21 2 or 4 Leu397Ala Phe420 Val 22 2 or 4 Leu397 Ser Phe420 Val 23 2 or 4 Leu397 ThrPhe420 Val 24 2 or 4 Leu397 Cys Phe420 Val 25 2 or 4 Leu397 Val Phe420Val 26 2 or 4 Leu397 Ile Phe420 Val 27 2 or 4 Leu397 Met Phe420 Val 28 2or 4 Leu397 Pro Phe420 Val 29 2 or 4 Leu397 Phe Phe420 Val 30 2 or 4Leu397 Tyr Phe420 Val 31 2 or 4 Leu397 Trp Phe420 Val 32 2 or 4 Leu397Asp Phe420 Val 33 2 or 4 Leu397 Glu Phe420 Val 34 2 or 4 Leu397 AsnPhe420 Val 35 2 or 4 Leu397 Gln Phe420 Val 36 2 or 4 Leu397 His Phe420Val 37 2 or 4 Leu397 Lys Phe420 Val 38 2 or 4 Leu397 Arg Phe420 Val

In a further particularly preferred embodiment, the variant orderivative of the mut-PPO of SEQ ID NO: 2 or SEQ ID NO: 4 is selectedfrom the combined amino acid substitutions of the following Table 3b.

TABLE 3b SEQ ID NO: 2 or SEQ ID NO: 4 (combined amino acidsubstitutions) Key amino Combination SEQ acid position Preferred NumberID NO: combination Substitution 39 2 or 4 Leu397 Asp, Glu, Gln, AsnLeu400 Ala, Ile, Val, Met 40 2 or 4 Leu397 Asp, Glu, Gln, Asn Phe457Met, Ala, Leu, Ile, Val 41 2 or 4 Phe204 Ala, Leu, Ile, Val Leu397 Asp,Glu, Gln, Asn 42 2 or 4 Thr208 Ser Leu400 Ala, Ile, Val, Met 43 2 or 4Leu400 Ala Phe457 Met, Ala, Leu, Ile, Val 44 2 or 4 Phe204 Ile Leu400Ala, Ile, Val, Met 45 2 or 4 The208 Ser Phe457 Met, Ala, Leu, Ile, Val46 2 or 4 Phe204 Ile Thr208 Ser 47 2 or 4 Phe204 Ile Phe457 Met, Ala,Leu, Ile, Val 48 2 or 4 Leu400 Ala, Ile, Val, Met Phe420 Val, Met, Ala,Ile, Leu 49 2 or 4 Phe204 Ile Phe420 Val, Met, Ala, Ile, Leu 50 2 or 4Phe420 Val, Met, Ala, Ile, Leu Phe457 Met, Ala, Leu, Ile, Val 51 2 or 4Arg128 Ala, Leu, Ile, Val Leu397 Asp, Glu, Gln, Asn 52 2 or 4 Thr208 SerLeu397 Asp, Glu, Gln, Asn Phe457 Met, Ala, Leu, Ile, Val 53 2 or 4Phe204 Ile The208 Ser Leu397 Asp, Glu, Gln, Asn 54 2 or 4 Phe204 IleLeu397 Asp, Glu, Gln, Asn Phe457 Met, Ala, Leu, Ile, Val 55 2 or 4Thr208 Ser Leu400 Ala, Ile, Val, Met Phe457 Met, Ala, Leu, Ile, Val 56 2or 4 Phe204 Ile Thr208 Ser Leu400 Ala, Ile, Val, Met 57 2 or 4 Phe204Ile Leu400 Ala, Ile, Val, Met Phe457 Met, Ala, Leu, Ile, Val 58 2 or 4Thr208 Ser Leu397 Asp, Glu, Gln, Asn Leu400 Ala, Ile, Val, Met 59 2 or 4Leu397 Asp, Glu, Gln, Asn Leu400 Ala, Ile, Val, Met Phe457 Met, Ala,Leu, Ile, Val 60 2 or 4 Phe204 Ile Leu397 Asp, Glu, Gln, Asn Leu400 Ala,Ile, Val, Met 61 2 or 4 Phe204 Ile Thr208 Ser Phe457 Met, Ala, Leu, Ile,Val 62 2 or 4 Leu397 Asp, Glu, Gln, Asn Leu400 Ala, Ile, Val, Met Phe420Met, Ala, Leu, Ile, Val 63 2 or 4 Leu397 Asp, Glu, Gln, Asn Phe420 Met,Ala, Leu, Ile, Val Phe457 Met, Ala, Leu, Ile, Val 64 2 or 4 Phe204 IleLeu397 Asp, Glu, Gln, Asn Phe420 Met, Ala, Leu, Ile, Val 65 2 or 4Phe204 Ile Thr208 Ser Phe420 Met, Ala, Leu, Ile, Val 66 2 or 4 Thr208Ser Phe420 Met, Ala, Leu, Ile, Val Phe457 Met, Ala, Leu, Ile, Val 67 2or 4 Phe204 Ile Phe420 Met, Ala, Leu, Ile, Val Phe457 Met, Ala, Leu,Ile, Val 68 2 or 4 Arg128 Ala, Leu, Ile, Val Leu400 Ala, Ile, Val, MetPhe420 Met, Ala, Leu, Ile, Val 69 2 or 4 Arg128 Ala, Leu, Ile, ValLeu397 Asp, Glu, Gln, Asn Phe420 Met, Ala, Leu, Ile, Val 70 2 or 4Arg128 Ala, Leu, Ile, Val Phe204 Ile Phe420 Met, Ala, Leu, Ile, Val 71 2or 4 Arg128 Ala, Leu, Ile, Val Phe420 Met, Ala, Leu, Ile, Val Phe457Met, Ala, Leu, Ile, Val 72 2 or 4 Thr208 Ser Leu400 Ala, Ile, Val, MetPhe420 Met, Ala, Leu, Ile, Val 73 2 or 4 Leu400 Ala, Ile, Val, MetPhe420 Met, Ala, Leu, Ile, Val Phe457 Met, Ala, Leu, Ile, Val 74 2 or 4Phe204 Ile Leu400 Ala, Ile, Val, Met Phe420 Met, Ala, Leu, Ile, Val 75 2or 4 Phe204 Ile Thr208 Ser Leu400 Ala, Ile, Val, Met Phe457 Met, Ala,Leu, Ile, Val 76 2 or 4 Phe204 Ile Thr208 Ser Phe420 Met, Ala, Leu, Ile,Val Phe457 Met, Ala, Leu, Ile, Val 77 2 or 4 Arg128 Ala, Leu, Ile, ValPhe204 Ile Phe420 Met, Ala, Leu, Ile, Val Phe457 Met, Ala, Leu, Ile, Val78 2 or 4 Phe204 Ile Leu400 Ala, Ile, Val, Met Phe420 Met, Ala, Leu,Ile, Val Phe457 Met, Ala, Leu, Ile, Val 79 2 or 4 Phe204 Ile Thr208 SerLeu397 Asp, Glu, Gln, Asn Leu400 Ala, Ile, Val, Met 80 2 or 4 Phe204 IleThr208 Ser Leu400 Ala, Ile, Val, Met Phe420 Met, Ala, Leu, Ile, ValPhe457 Met, Ala, Leu, Ile, Val 81 2 or 4 Arg128 Ala, Leu, Ile, ValPhe204 Ile Leu400 Ala, Ile, Val, Met Phe420 Met, Ala, Leu, Ile, ValPhe457 Met, Ala, Leu, Ile, Val

It is to be understood that any amino acid besides the ones mentioned inthe above tables 3 could be used as a substitutent. Assays to test forthe functionality of such mutants are readily available in the art, andrespectively, described in the Example section of the present invention.

In a preferred embodiment, the amino acid sequence differs from an aminoacid sequence of a PPO of SEQ ID NO: 2 or SEQ ID NO: 4 at one or more ofthe following positions: 128, 204, 208, 397, 400, 420, 457.

Examples of differences at these amino acid positions include, but arenot limited to, one or more of the following:

the amino acid at position 128 is other than Arginine;

the amino acid at position 204 is other than Phenylalanine;

the amino acid at position 208 is other than Threonine;

the amino acid at position 397 is other than Leucine,

the amino acid at position 400 is other than Leucine,

the amino acid at position 420 is other than Phenylalanine,

the amino acid at position 457 is other than Phenylalanine.

In some embodiments, the mut-PPO enzyme of SEQ ID NO: 2 or SEQ ID NO: 4comprises one or more of the following:

the amino acid at position 128 is Leu, Ala, Val, or Ile;

the amino acid at position 204 is Ala, Leu, Ile, or Val;

the amino acid at position 208 is Ser;

the amino acid at position 397 is Gly, Ala, Ser, Thr, Cys, Val, Ile,Met, Pro, Phe, Tyr, Trp, His, Lys, Arg, Asn, Asp, Glu, or Gln;

the amino acid at position 400 is Ala, Ile, Val, or Met;

the amino acid at position 420 is Val, Met, Ala, Ile, or Leu;

the amino acid at position 457 is Met, Ala, Leu, Ile, Val;

In a preferred embodiment, the mut-PPO comprises a sequence of SEQ IDNO: 2 or SEQ ID NO:4, a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 420 is Met, and the the amino acid atposition 397 is Gly, Ala, Ser, Thr, Cys, Val, Ile, Met, Pro, Phe, Tyr,Trp, His, Lys, Arg, Asn, Asp, Glu, or Gln.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4, a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 420 is Val, and the the amino acid atposition 397 is Gly, Ala, Ser, Thr, Cys, Val, Ile, Met, Pro, Phe, Tyr,Trp, His, Lys, Arg, Asn, Asp, Glu, or Gln.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4, a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 397 is Asn, Asp, Glu, or Gln, and the aminoacid at position 400 is Ala, Ile, Val, or Met.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4, a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 397 is Asn, Asp, Glu, or Gln, and the aminoacid at position 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4, a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, and the aminoacid at position 397 is Asn, Asp, Glu, or Gln.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 208 is Ser, and the amino acid at position400 is Ala, Ile, Val, or Met.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 400 is Ala, Ile, Val, or Met, and the aminoacid at position 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, and the aminoacid at position 400 is Ala, Ile, Val, or Met.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 208 is Ser, and the amino acid at position457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, and the aminoacid at position 208 is Ser.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, and the aminoacid at position 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 400 is Ala, Ile, Val, or Met, and the aminoacid at position 420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, and the aminoacid at position 420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 420 is Val, Met, Ala, Ile, or Leu, and theamino acid at position 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 128 is Leu, Ala, Val, or Ile, and the aminoacid at position 397 is Asn, Asp, Glu, or Gln.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 208 is Ser, the amino acid at position 397 isAsn, Asp, Glu, or Gln, and the amino acid at position 457 is Met, Ala,Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, and the amino acid at position 397 is Asn, Asp,Glu, or Gln.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 397 is Asn, Asp, Glu, or Gln, and the amino acid at position457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 208 is Ser, the amino acid at position 400 isAla, Ile, Val, or Met, and the amino acid at position 457 is Met, Ala,Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, and

the amino acid at position 400 is Ala, Ile, Val, or Met.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 400 is Ala, Ile, Val, or Met, and the amino acid at position457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 208 is Ser, the amino acid at position 397 isAsn, Asp, Glu, or Gln, and the amino acid at position 400 is Ala, Ile,Val, or Met.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 397 is Asn, Asp, Glu, or Gln, the amino acidat position 400 is Ala, Ile, Val, or Met, and the amino acid at position457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 397 is Asn, Asp, Glu, or Gln, and the amino acid at position400 is Ala, Ile, Val, or Met.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, and

the amino acid at position 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 397 is Asn, Asp, Glu, or Gln, the amino acidat position 400 is Ala, Ile, Val, or Met, and the amino acid at position420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 397 is Asn, Asp, Glu, or Gln, the amino acidat position 420 is Val, Met, Ala, Ile, or Leu, and the amino acid atposition 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 397 is Asn, Asp, Glu, or Gln, and the amino acid at position420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, and

the amino acid at position 420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 208 is Ser, the amino acid at position 420 isVal, Met, Ala, Ile, or Leu, and the amino acid at position 457 is Met,Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 420 is Val, Met, Ala, Ile, or Leu, and the amino acid atposition 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 128 is Leu, Ala, Val, or Ile, the amino acidat position 400 is Ala, Ile, Val, or Met, and the amino acid at position420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 128 is Leu, Ala, Val, or Ile, the amino acidat position 397 is Asn, Asp, Glu, or Gln, and the amino acid at position420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 128 is Leu, Ala, Val, or Ile, the amino acidat position 204 is Ala, Leu, Ile, or Val, and the amino acid at position420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 128 is Leu, Ala, Val, or Ile, the amino acidat position 420 is Val, Met, Ala, Ile, or Leu, and the amino acid atposition 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 208 is Ser, the amino acid at position 400 isAla, Ile, Val, or Met, and the amino acid at position 420 is Val, Met,Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 400 is Ala, Ile, Val, or Met, the amino acidat position 420 is Val, Met, Ala, Ile, or Leu, and the amino acid atposition 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 400 is Ala, Ile, Val, or Met, and the amino acid at position420 is Val, Met, Ala, Ile, or Leu.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, the amino acid at position 400 is Ala, Ile, Val,or Met, and the amino acid at position 457 is Met, Ala, Leu, Ile, orVal.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, the amino acid at position 420 is Val, Met, Ala,Ile, or Leu, and the amino acid at position 457 is Met, Ala, Leu, Ile,or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 128 is Leu, Ala, Val, or Ile, the amino acidat position 204 is Ala, Leu, Ile, or Val, the amino acid at position 420is Val, Met, Ala, Ile, or Leu, and the amino acid at position 457 isMet, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 400 is Ala, Ile, Val, or Met, the amino acid at position 420is Val, Met, Ala, Ile, or Leu, and the amino acid at position 457 isMet, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, the amino acid at position 397 is Asn, Asp, Glu,or Gln, and the amino acid at position 400 is Ala, Ile, Val, or Met.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 204 is Ala, Leu, Ile, or Val, the amino acidat position 208 is Ser, the amino acid at position 400 is Ala, Ile, Val,or Met, the amino acid at position 420 is Val, Met, Ala, Ile, or Leu,and the amino acid at position 457 is Met, Ala, Leu, Ile, or Val.

In another preferred embodiment, the mut-PPO comprises a sequence of SEQID NO: 2 or SEQ ID NO:4 a variant, derivative, orthologue, paralogue orhomologue thereof, in which:

the amino acid at position 128 is Leu, Ala, Val, or Ile, the amino acidat position 204 is Ala, Leu, Ile, or Val, the amino acid at position 400is Ala, Ile, Val, or Met, the amino acid at position 420 is Val, Met,Ala, Ile, or Leu, and the amino acid at position 457 is Met, Ala, Leu,Ile, or Val.

It will be within the knowledge of the skilled artisan to identifyconserved regions and motifs shared between the homologues, orthologuesand paralogues encoded by SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19,21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, or 45, such as thosedepicted in Table 1. Having identified such conserved regions that mayrepresent suitable binding motifs, amino acids corresponding to theamino acids listed in Table 3a and 3b, can be chosen to be subsituted byany other amino acid, preferably by conserved amino acids as shown intable 2, and more preferably by the amino acids of tables 3a and 3b.

In addition, the present invention refers to a method for identifying abenzoxazinone-derivative herbicide by using a mut-PPO encoded by anucleic acid which comprises the nucleotide sequence of SEQ ID NO: 1, 3,5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41,43, or 45, or a variant or derivative thereof.

Said method comprises the steps of:

-   -   a) generating a transgenic cell or plant comprising a nucleic        acid encoding a mut-PPO, wherein the mut-PPO is expressed;    -   b) applying a benzoxazinone-derivative herbicide to the        transgenic cell or plant of a) and to a control cell or plant of        the same variety;    -   c) determining the growth or the viability of the transgenic        cell or plant and the control cell or plant after application of        said benzoxazinone-derivative herbicide, and    -   d) selecting “benzoxazinone-derivative herbicides” which confer        reduced growth to the control cell or plant as compared to the        growth of the transgenic cell or plant.

By “control cell” or “similar, wild-type, plant, plant tissue, plantcell or host cell” is intended a plant, plant tissue, plant cell, orhost cell, respectively, that lacks the herbicide-resistancecharacteristics and/or particular polynucleotide of the invention thatare disclosed herein. The use of the term “wild-type” is not, therefore,intended to imply that a plant, plant tissue, plant cell, or other hostcell lacks recombinant DNA in its genome, and/or does not possessherbicide-resistant characteristics that are different from thosedisclosed herein.

Another object refers to a method of identifying a nucleotide sequenceencoding a mut-PPO which is resistant or tolerant to abenzoxazinone-derivative herbicide, the method comprising:

-   -   a) generating a library of mut-PPO-encoding nucleic acids,    -   b) screening a population of the resulting mut-PPO-encoding        nucleic acids by expressing each of said nucleic acids in a cell        or plant and treating said cell or plant with a        benzoxazinone-derivative herbicide,    -   c) comparing the benzoxazinone-derivative herbicide-tolerance        levels provided by said population of mut-PPO encoding nucleic        acids with the benzoxazinone-derivative herbicide-tolerance        level provided by a control PPO-encoding nucleic acid,    -   d) selecting at least one mut-PPO-encoding nucleic acid that        provides a significantly increased level of tolerance to a        benzoxazinone-derivative herbicide as compared to that provided        by the control PPO-encoding nucleic acid.

In a preferred embodiment, the mut-PPO-encoding nucleic acid selected instep d) provides at least 2-fold as much resistance or tolerance of acell or plant to a benzoxazinone-derivative herbicide as compared tothat provided by the control PPO-encoding nucleic acid.

In a further preferred embodiment, the mut-PPO-encoding nucleic acidselected in step d) provides at least 2-fold, at least 5-fold, at least10-fold, at least 20-fold, at least 50-fold, at least 100-fold, at least500-fold, as much resistance or tolerance of a cell or plant to abenzoxazinone-derivative herbicide as compared to that provided by thecontrol PPO-encoding nucleic acid.

The resistance or tolerance can be determined by generating a transgenicplant or host cell, preferably a plant cell, comprising a nucleic acidsequence of the library of step a) and comparing said transgenic plantwith a control plant or host cell, preferably a plant cell.

Another object refers to a method of identifying a plant or algaecontaining a nucleic acid comprising a nucleotide sequence encoding awild-type or mut-PPO which is resistant or tolerant to abenzoxazinone-derivative herbicide, the method comprising:

-   -   a) identifying an effective amount of a benzoxazinone-derivative        herbicide in a culture of plant cells or green algae that leads        to death of said cells.    -   b) treating said plant cells or green algae with a mutagenizing        agent,    -   c) contacting said mutagenized cells population with an        effective amount of benzoxazinone-derivative herbicide,        identified in a),    -   d) selecting at least one cell surviving these test conditions,    -   e) PCR-amplification and sequencing of PPO genes from cells        selected in d) and comparing such sequences to wild-type PPO        gene sequences, respectively.

In a preferred embodiment, said mutagenizing agent isethylmethanesulfonate (EMS).

Many methods well known to the skilled artisan are available forobtaining suitable candidate nucleic acids for identifying a nucleotidesequence encoding a mut-PPO from a variety of different potential sourceorganisms including microbes, plants, fungi, algae, mixed cultures etc.as well as environmental sources of DNA such as soil. These methodsinclude inter alia the preparation of cDNA or genomic DNA libraries, theuse of suitably degenerate oligonucleotide primers, the use of probesbased upon known sequences or complementation assays (for example, forgrowth upon tyrosine) as well as the use of mutagenesis and shuffling inorder to provide recombined or shuffled mut-PPO-encoding sequences.

Nucleic acids comprising candidate and control PPO encoding sequencescan be expressed in yeast, in a bacterial host strain, in an alga or ina higher plant such as tobacco or Arabidopsis and the relative levels ofinherent tolerance of the PPO encoding sequences screened according to avisible indicator phenotype of the transformed strain or plant in thepresence of different concentrations of the selectedbenzoxazinone-derivative herbicide. Dose responses and relative shiftsin dose responses associated with these indicator phenotypes (formationof brown color, growth inhibition, herbicidal effect etc) areconveniently expressed in terms, for example, of GR50 (concentration for50% reduction of growth) or MIC (minimum inhibitory concentration)values where increases in values correspond to increases in inherenttolerance of the expressed PPO. For example, in a relatively rapid assaysystem based upon transformation of a bacterium such as E. coli, eachmut-PPO encoding sequence may be expressed, for example, as a DNAsequence under expression control of a controllable promoter such as thelacZ promoter and taking suitable account, for example by the use ofsynthetic DNA, of such issues as codon usage in order to obtain ascomparable a level of expression as possible of different PPO sequences.Such strains expressing nucleic acids comprising alternative candidatePPO sequences may be plated out on different concentrations of theselected benzoxazinone-derivative herbicide in, optionally, a tyrosinesupplemented medium and the relative levels of inherent tolerance of theexpressed PPO enzymes estimated on the basis of the extent and MIC forinhibition of the formation of the brown, ochronotic pigment.

In another embodiment, candidate nucleic acids are transformed intoplant material to generate a transgenic plant, regenerated intomorphologically normal fertile plants which are then measured fordifferential tolerance to selected benzoxazinone-derivative herbicides.Many suitable methods for transformation using suitable selectionmarkers such as kanamycin, binary vectors such as from Agrobacterium andplant regeneration as, for example, from tobacco leaf discs are wellknown in the art. Optionally, a control population of plants is likewisetransformed with a nucleic acid expressing the control PPO.Alternatively, an untransformed dicot plant such as Arabidopsis orTobacco can be used as a control since this, in any case, expresses itsown endogenous PPO. The average, and distribution, of herbicidetolerance levels of a range of primary plant transformation events ortheir progeny to benzoxazinone-derivative described supra are evaluatedin the normal manner based upon plant damage, meristematic bleachingsymptoms etc. at a range of different concentrations of herbicides.These data can be expressed in terms of, for example, GR50 valuesderived from dose/response curves having “dose” plotted on the x-axisand “percentage kill”, “herbicidal effect”, “numbers of emerging greenplants” etc. plotted on the y-axis where increased GR50 valuescorrespond to increased levels of inherent tolerance of the expressedPPO. Herbicides can suitably be applied pre-emergence or post-emergence.

Another object refers to an isolated nucleic acid encoding a mut-PPO,wherein the nucleic acid is identifiable by a method as defined above.

In another embodiment, the invention refers to a plant cell transformedby a wild-type or a mut-PPO nucleic acid or or a plant cell which hasbeen mutated to obtain a plant expressing a wild-type or a mut-PPOnucleic acid, wherein expression of the nucleic acid in the plant cellresults in increased resistance or tolerance to abenzoxazinone-derivative herbicide as compared to a wild type variety ofthe plant cell.

The term “expression/expressing” or “gene expression” means thetranscription of a specific gene or specific genes or specific geneticconstruct. The term “expression” or “gene expression” in particularmeans the transcription of a gene or genes or genetic construct intostructural RNA (rRNA, tRNA) or mRNA with or without subsequenttranslation of the latter into a protein. The process includestranscription of DNA and processing of the resulting mRNA product.

To obtain the desired effect, i.e. plants that are tolerant or resistantto the benzoxazinone-derivative herbicide derivative herbicide of thepresent invention, it will be understood that the at least one nucleicacid is “over-expressed” by methods and means known to the personskilled in the art.

The term “increased expression” or “overexpression” as used herein meansany form of expression that is additional to the original wild-typeexpression level. Methods for increasing expression of genes or geneproducts are well documented in the art and include, for example,overexpression driven by appropriate promoters, the use of transcriptionenhancers or translation enhancers. Isolated nucleic acids which serveas promoter or enhancer elements may be introduced in an appropriateposition (typically upstream) of a non-heterologous form of apolynucleotide so as to upregulate expression of a nucleic acid encodingthe polypeptide of interest. For example, endogenous promoters may bealtered in vivo by mutation, deletion, and/or substitution (see, Kmiec,U.S. Pat. No. 5,565,350; Zarling et al., WO9322443), or isolatedpromoters may be introduced into a plant cell in the proper orientationand distance from a gene of the present invention so as to control theexpression of the gene.

If polypeptide expression is desired, it is generally desirable toinclude a polyadenylation region at the 3′-end of a polynucleotidecoding region. The polyadenylation region can be derived from thenatural gene, from a variety of other plant genes, or from T-DNA. The 3′end sequence to be added may be derived from, for example, the nopalinesynthase or octopine synthase genes, or alternatively from another plantgene, or less preferably from any other eukaryotic gene.

An intron sequence may also be added to the 5′ untranslated region (UTR)or the coding sequence of the partial coding sequence to increase theamount of the mature message that accumulates in the cytosol. Inclusionof a spliceable intron in the transcription unit in both plant andanimal expression constructs has been shown to increase gene expressionat both the mRNA and protein levels up to 1000-fold (Buchman and Berg(1988) Mol. Cell biol. 8: 4395-4405; Callis et al. (1987) Genes Dev1:1183-1200). Such intron enhancement of gene expression is typicallygreatest when placed near the 5′ end of the transcription unit. Use ofthe maize introns Adh1-S intron 1, 2, and 6, the Bronze-1 intron areknown in the art. For general information see: The Maize Handbook,Chapter 116, Freeling and Walbot, Eds., Springer, N.Y. (1994)

The term “introduction” or “transformation” as referred to hereinencompasses the transfer of an exogenous polynucleotide into a hostcell, irrespective of the method used for transfer. Plant tissue capableof subsequent clonal propagation, whether by organogenesis orembryogenesis, may be transformed with a genetic construct of thepresent invention and a whole plant regenerated there from. Theparticular tissue chosen will vary depending on the clonal propagationsystems available for, and best suited to, the particular species beingtransformed. Exemplary tissue targets include leaf disks, pollen,embryos, cotyledons, hypocotyls, megagametophytes, callus tissue,existing meristematic tissue (e.g., apical meristem, axillary buds, androot meristems), and induced meristem tissue (e.g., cotyledon meristemand hypocotyl meristem). The polynucleotide may be transiently or stablyintroduced into a host cell and may be maintained non-integrated, forexample, as a plasmid. Alternatively, it may be integrated into the hostgenome. The resulting transformed plant cell may then be used toregenerate a transformed plant in a manner known to persons skilled inthe art.

The transfer of foreign genes into the genome of a plant is calledtransformation. Transformation of plant species is now a fairly routinetechnique. Advantageously, any of several transformation methods may beused to introduce the gene of interest into a suitable ancestor cell.The methods described for the transformation and regeneration of plantsfrom plant tissues or plant cells may be utilized for transient or forstable transformation. Transformation methods include the use ofliposomes, electroporation, chemicals that increase free DNA uptake,injection of the DNA directly into the plant, particle gun bombardment,transformation using viruses or pollen and microprojection. Methods maybe selected from the calcium/polyethylene glycol method for protoplasts(Krens, F. A. et al., (1982) Nature 296, 72-74; Negrutiu I et al. (1987)Plant Mol Biol 8: 363-373); electroporation of protoplasts (Shillito R.D. et al. (1985) Bio/Technol 3, 1099-1102); microinjection into plantmaterial (Crossway A et al., (1986) Mol. Gen Genet 202: 179-185); DNA orRNA-coated particle bombardment (Klein T M et al., (1987) Nature 327:70) infection with (non-integrative) viruses and the like. Transgenicplants, including transgenic crop plants, are preferably produced viaAgrobacterium-mediated transformation. An advantageous transformationmethod is the transformation in planta. To this end, it is possible, forexample, to allow the agrobacteria to act on plant seeds or to inoculatethe plant meristem with agrobacteria. It has proved particularlyexpedient in accordance with the invention to allow a suspension oftransformed agrobacteria to act on the intact plant or at least on theflower primordia. The plant is subsequently grown on until the seeds ofthe treated plant are obtained (Clough and Bent, Plant J. (1998) 16,735-743). Methods for Agrobacterium-mediated transformation of riceinclude well known methods for rice transformation, such as thosedescribed in any of the following: European patent application EP1198985 A1, Aldemita and Hodges (Planta 199: 612-617, 1996); Chan et al.(Plant Mol Biol 22 (3): 491-506, 1993), Hiei et al. (Plant J 6 (2):271-282, 1994), which disclosures are incorporated by reference hereinas if fully set forth. In the case of corn transformation, the preferredmethod is as described in either Ishida et al. (Nat. Biotechnol 14(6):745-50, 1996) or Frame et al. (Plant Physiol 129(1): 13-22, 2002), whichdisclosures are incorporated by reference herein as if fully set forth.Said methods are further described by way of example in B. Jenes et al.,Techniques for Gene Transfer, in: Transgenic Plants, Vol. 1, Engineeringand Utilization, eds. S. D. Kung and R. Wu, Academic Press (1993)128-143 and in Potrykus Annu. Rev. Plant Physiol. Plant Molec. Biol. 42(1991) 205-225). The nucleic acids or the construct to be expressed ispreferably cloned into a vector, which is suitable for transformingAgrobacterium tumefaciens, for example pBin19 (Bevan et al., Nucl. AcidsRes. 12 (1984) 8711). Agrobacteria transformed by such a vector can thenbe used in known manner for the transformation of plants, such as plantsused as a model, like Arabidopsis (Arabidopsis thaliana is within thescope of the present invention not considered as a crop plant), or cropplants such as, by way of example, tobacco plants, for example byimmersing bruised leaves or chopped leaves in an agrobacterial solutionand then culturing them in suitable media. The transformation of plantsby means of Agrobacterium tumefaciens is described, for example, byHöfgen and Willmitzer in Nucl. Acid Res. (1988) 16, 9877 or is knowninter alia from F. F. White, Vectors for Gene Transfer in Higher Plants;in Transgenic Plants, Vol. 1, Engineering and Utilization, eds. S. D.Kung and R. Wu, Academic Press, 1993, pp. 15-38.

In addition to the transformation of somatic cells, which then have tobe regenerated into intact plants, it is also possible to transform thecells of plant meristems and in particular those cells which developinto gametes. In this case, the transformed gametes follow the naturalplant development, giving rise to transgenic plants. Thus, for example,seeds of Arabidopsis are treated with agrobacteria and seeds areobtained from the developing plants of which a certain proportion istransformed and thus transgenic [Feldman, K A and Marks M D (1987). MolGen Genet 208:274-289; Feldmann K (1992). In: C Koncz, N-H Chua and JShell, eds, Methods in Arabidopsis Research. Word Scientific, Singapore,pp. 274-289]. Alternative methods are based on the repeated removal ofthe inflorescences and incubation of the excision site in the center ofthe rosette with transformed agrobacteria, whereby transformed seeds canlikewise be obtained at a later point in time (Chang (1994). Plant J. 5:551-558; Katavic (1994). Mol Gen Genet, 245: 363-370). However, anespecially effective method is the vacuum infiltration method with itsmodifications such as the “floral dip” method. In the case of vacuuminfiltration of Arabidopsis, intact plants under reduced pressure aretreated with an agrobacterial suspension [Bechthold, N (1993). C R AcadSci Paris Life Sci, 316: 1194-1199], while in the case of the “floraldip” method the developing floral tissue is incubated briefly with asurfactant-treated agrobacterial suspension [Clough, S J and Bent A F(1998) The Plant J. 16, 735-743]. A certain proportion of transgenicseeds are harvested in both cases, and these seeds can be distinguishedfrom non-transgenic seeds by growing under the above-described selectiveconditions. In addition the stable transformation of plastids is ofadvantages because plastids are inherited maternally is most cropsreducing or eliminating the risk of transgene flow through pollen. Thetransformation of the chloroplast genome is generally achieved by aprocess which has been schematically displayed in Klaus et al., 2004[Nature Biotechnology 22 (2), 225-229]. Briefly the sequences to betransformed are cloned together with a selectable marker gene betweenflanking sequences homologous to the chloroplast genome. Thesehomologous flanking sequences direct site specific integration into theplastome. Plastidal transformation has been described for many differentplant species and an overview is given in Bock (2001) Transgenicplastids in basic research and plant biotechnology. J Mol Biol. 2001Sep. 21; 312 (3):425-38 or Maliga, P (2003) Progress towardscommercialization of plastid transformation technology. TrendsBiotechnol. 21, 20-28. Further biotechnological progress has recentlybeen reported in form of marker free plastid transformants, which can beproduced by a transient co-integrated maker gene (Klaus et al., 2004,Nature Biotechnology 22(2), 225-229). The genetically modified plantcells can be regenerated via all methods with which the skilled workeris familiar. Suitable methods can be found in the abovementionedpublications by S. D. Kung and R. Wu, Potrykus or Höfgen and Willmitzer.

Generally after transformation, plant cells or cell groupings areselected for the presence of one or more markers which are encoded byplant-expressible genes co-transferred with the gene of interest,following which the transformed material is regenerated into a wholeplant. To select transformed plants, the plant material obtained in thetransformation is, as a rule, subjected to selective conditions so thattransformed plants can be distinguished from untransformed plants. Forexample, the seeds obtained in the above-described manner can be plantedand, after an initial growing period, subjected to a suitable selectionby spraying. A further possibility consists in growing the seeds, ifappropriate after sterilization, on agar plates using a suitableselection agent so that only the transformed seeds can grow into plants.Alternatively, the transformed plants are screened for the presence of aselectable marker such as the ones described above.

Following DNA transfer and regeneration, putatively transformed plantsmay also be evaluated, for instance using Southern analysis, for thepresence of the gene of interest, copy number and/or genomicorganisation. Alternatively or additionally, expression levels of thenewly introduced DNA may be monitored using Northern and/or Westernanalysis, both techniques being well known to persons having ordinaryskill in the art.

The generated transformed plants may be propagated by a variety ofmeans, such as by clonal propagation or classical breeding techniques.For example, a first generation (or T1) transformed plant may be selfedand homozygous second-generation (or T2) transformants selected, and theT2 plants may then further be propagated through classical breedingtechniques. The generated transformed organisms may take a variety offorms. For example, they may be chimeras of transformed cells andnon-transformed cells; clonal transformants (e.g., all cells transformedto contain the expression cassette); grafts of transformed anduntransformed tissues (e.g., in plants, a transformed rootstock graftedto an untransformed scion).

Preferably, the wild-type or mut-PPO nucleic acid comprises apolynucleotide sequence selected from the group consisting of: a) apolynucleotide as shown in SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19,21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, or 45, ora variant orderivative thereof; b) a polynucleotide encoding a polypeptide as shownin SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30,32, 34, 36, 38, 40, 42, 44, or 46, or a variant or derivative thereof;c) a polynucleotide comprising at least 60 consecutive nucleotides ofany of a) or b); and d) a polynucleotide complementary to thepolynucleotide of any of a) through c).

Preferably, the expression of the nucleic acid in the plant results inthe plant's increased resistance to benzoxazinone-derivative herbicideas compared to a wild type variety of the plant.

In another embodiment, the invention refers to a plant, preferably atransgenic plant, comprising a plant cell according to the presentinvention, wherein expression of the nucleic acid in the plant resultsin the plant's increased resistance to benzoxazinone-derivativeherbicide as compared to a wild type variety of the plant.

The plants described herein can be either transgenic crop plants ornon-transgenic plants.

For the purposes of the invention, “transgenic”, “transgene” or“recombinant” means with regard to, for example, a nucleic acidsequence, an expression cassette, gene construct or a vector comprisingthe nucleic acid sequence or an organism transformed with the nucleicacid sequences, expression cassettes or vectors according to theinvention, all those constructions brought about by recombinant methodsin which either

-   -   (a) the nucleic acid sequences encoding proteins useful in the        methods of the invention, or    -   (b) genetic control sequence(s) which is operably linked with        the nucleic acid sequence according to the invention, for        example a promoter, or    -   (c) a) and b)

are not located in their natural genetic environment or have beenmodified by recombinant methods, it being possible for the modificationto take the form of, for example, a substitution, addition, deletion,inversion or insertion of one or more nucleotide residues. The naturalgenetic environment is understood as meaning the natural genomic orchromosomal locus in the original plant or the presence in a genomiclibrary. In the case of a genomic library, the natural geneticenvironment of the nucleic acid sequence is preferably retained, atleast in part. The environment flanks the nucleic acid sequence at leaston one side and has a sequence length of at least 50 bp, preferably atleast 500 bp, especially preferably at least 1000 bp, most preferably atleast 5000 bp. A naturally occurring expression cassette—for example thenaturally occurring combination of the natural promoter of the nucleicacid sequences with the corresponding nucleic acid sequence encoding apolypeptide useful in the methods of the present invention, as definedabove—becomes a transgenic expression cassette when this expressioncassette is modified by non-natural, synthetic (“artificial”) methodssuch as, for example, mutagenic treatment. Suitable methods aredescribed, for example, in U.S. Pat. No. 5,565,350 or WO 00/15815.

A transgenic plant for the purposes of the invention is thus understoodas meaning, as above, that the nucleic acids used in the method of theinvention are not at their natural locus in the genome of said plant, itbeing possible for the nucleic acids to be expressed homologously orheterologously. However, as mentioned, transgenic also means that, whilethe nucleic acids according to the invention or used in the inventivemethod are at their natural position in the genome of a plant, thesequence has been modified with regard to the natural sequence, and/orthat the regulatory sequences of the natural sequences have beenmodified. Transgenic is preferably understood as meaning the expressionof the nucleic acids according to the invention at an unnatural locus inthe genome, i.e. homologous or, preferably, heterologous expression ofthe nucleic acids takes place. Preferred transgenic plants are mentionedherein. Furthermore, the term “transgenic” refers to any plant, plantcell, callus, plant tissue, or plant part, that contains all or part ofat least one recombinant polynucleotide. In many cases, all or part ofthe recombinant polynucleotide is stably integrated into a chromosome orstable extra-chromosomal element, so that it is passed on to successivegenerations. For the purposes of the invention, the term “recombinantpolynucleotide” refers to a polynucleotide that has been altered,rearranged, or modified by genetic engineering. Examples include anycloned polynucleotide, or polynucleotides, that are linked or joined toheterologous sequences. The term “recombinant” does not refer toalterations of polynucleotides that result from naturally occurringevents, such as spontaneous mutations, or from non-spontaneousmutagenesis followed by selective breeding.

Plants containing mutations arising due to non-spontaneous mutagenesisand selective breeding are referred to herein as non-transgenic plantsand are included in the present invention. In embodiments wherein theplant is transgenic and comprises multiple mut-PPO nucleic acids, thenucleic acids can be derived from different genomes or from the samegenome. Alternatively, in embodiments wherein the plant isnon-transgenic and comprises multiple mut-PPO nucleic acids, the nucleicacids are located on different genomes or on the same genome.

In certain embodiments, the present invention involvesherbidicide-resistant plants that are produced by mutation breeding.Such plants comprise a polynucleotide encoding a mut-PPO and aretolerant to one or more “benzoxazinone-derivative herbicides”. Suchmethods can involve, for example, exposing the plants or seeds to amutagen, particularly a chemical mutagen such as, for example, ethylmethanesulfonate (EMS) and selecting for plants that have enhancedtolerance to at least one or more benzoxazinone-derivative herbicide.

However, the present invention is not limited to herbicide-tolerantplants that are produced by a mutagenesis method involving the chemicalmutagen EMS. Any mutagenesis method known in the art may be used toproduce the herbicide-resistant plants of the present invention. Suchmutagenesis methods can involve, for example, the use of any one or moreof the following mutagens: radiation, such as X-rays, Gamma rays (e.g.,cobalt 60 or cesium 137), neutrons, (e.g., product of nuclear fission byuranium 235 in an atomic reactor), Beta radiation (e.g., emitted fromradioisotopes such as phosphorus 32 or carbon 14), and ultravioletradiation (preferably from 2500 to 2900 nm), and chemical mutagens suchas base analogues (e.g., 5-bromo-uracil), related compounds (e.g.,8-ethoxy caffeine), antibiotics (e.g., streptonigrin), alkylating agents(e.g., sulfur mustards, nitrogen mustards, epoxides, ethylenamines,sulfates, sulfonates, sulfones, lactones), azide, hydroxylamine, nitrousacid, or acridines. Herbicide-resistant plants can also be produced byusing tissue culture methods to select for plant cells comprisingherbicide-resistance mutations and then regenerating herbicide-resistantplants therefrom. See, for example, U.S. Pat. Nos. 5,773,702 and5,859,348, both of which are herein incorporated in their entirety byreference. Further details of mutation breeding can be found in“Principals of Cultivar Development” Fehr, 1993 Macmillan PublishingCompany the disclosure of which is incorporated herein by reference

In addition to the definition above, the term “plant” is intended toencompass crop plants at any stage of maturity or development, as wellas any tissues or organs (plant parts) taken or derived from any suchplant unless otherwise clearly indicated by context. Plant partsinclude, but are not limited to, stems, roots, flowers, ovules, stamens,leaves, embryos, meristematic regions, callus tissue, anther cultures,gametophytes, sporophytes, pollen, microspores, protoplasts, and thelike.

The plant of the present invention comprises at least one mut-PPOnucleic acid or over-expressed wild-type PPO nucleic acid, and hasincreased tolerance to a benzoxazinone-derivative herbicide as comparedto a wild-type variety of the plant. It is possible for the plants ofthe present invention to have multiple wild-type or mut-PPO nucleicacids from different genomes since these plants can contain more thanone genome. For example, a plant contains two genomes, usually referredto as the A and B genomes. Because PPO is a required metabolic enzyme,it is assumed that each genome has at least one gene coding for the PPOenzyme (i.e. at least one PPO gene). As used herein, the term “PPO genelocus” refers to the position of an PPO gene on a genome, and the terms“PPO gene” and “PPO nucleic acid” refer to a nucleic acid encoding thePPO enzyme. The PPO nucleic acid on each genome differs in itsnucleotide sequence from an PPO nucleic acid on another genome. One ofskill in the art can determine the genome of origin of each PPO nucleicacid through genetic crossing and/or either sequencing methods orexonuclease digestion methods known to those of skill in the art.

The present invention includes plants comprising one, two, three, ormore mut-PPO alleles, wherein the plant has increased tolerance to abenzoxazinone-derivative herbicide as compared to a wild-type variety ofthe plant. The mut-PPO alleles can comprise a nucleotide sequenceselected from the group consisting of a polynucleotide as defined in SEQID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33,35, 37, 39, 41, 43, or 45, or a variant or derivative thereof, apolynucleotide encoding a polypeptide as defined in SEQ ID NO: 2, 4, 6,8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42,44, or 46, or a variant or derivative, homologue, orthologue, paraloguethereof, a polynucleotide comprising at least 60 consecutive nucleotidesof any of the aforementioned polynucleotides; and a polynucleotidecomplementary to any of the aforementioned polynucleotides.

“Alleles” or “allelic variants” are alternative forms of a given gene,located at the same chromosomal position. Allelic variants encompassSingle Nucleotide Polymorphisms (SNPs), as well as SmallInsertion/Deletion Polymorphisms (INDELs). The size of INDELs is usuallyless than 100 bp. SNPs and INDELs form the largest set of sequencevariants in naturally occurring polymorphic strains of most organisms

The term “variety” refers to a group of plants within a species definedby the sharing of a common set of characteristics or traits accepted bythose skilled in the art as sufficient to distinguish one cultivar orvariety from another cultivar or variety. There is no implication ineither term that all plants of any given cultivar or variety will begenetically identical at either the whole gene or molecular level orthat any given plant will be homozygous at all loci. A cultivar orvariety is considered “true breeding” for a particular trait if, whenthe true-breeding cultivar or variety is self-pollinated, all of theprogeny contain the trait. The terms “breeding line” or “line” refer toa group of plants within a cultivar defined by the sharing of a commonset of characteristics or traits accepted by those skilled in the art assufficient to distinguish one breeding line or line from anotherbreeding line or line. There is no implication in either term that allplants of any given breeding line or line will be genetically identicalat either the whole gene or molecular level or that any given plant willbe homozygous at all loci. A breeding line or line is considered “truebreeding” for a particular trait if, when the true-breeding line orbreeding line is self-pollinated, all of the progeny contain the trait.In the present invention, the trait arises from a mutation in a PPO geneof the plant or seed.

The herbicide-resistant plants of the invention that comprisepolynucleotides encoding mut-PPO polypeptides also find use in methodsfor increasing the herbicide-resistance of a plant through conventionalplant breeding involving sexual reproduction. The methods comprisecrossing a first plant that is a herbicide-resistant plant of theinvention to a second plant that may or may not be resistant to the sameherbicide or herbicides as the first plant or may be resistant todifferent herbicide or herbicides than the first plant. The second plantcan be any plant that is capable of producing viable progeny plants(i.e., seeds) when crossed with the first plant. Typically, but notnecessarily, the first and second plants are of the same species. Themethods can optionally involve selecting for progeny plants thatcomprise the mut-PPO polypeptides of the first plant and the herbicideresistance characteristics of the second plant. The progeny plantsproduced by this method of the present invention have increasedresistance to a herbicide when compared to either the first or secondplant or both. When the first and second plants are resistant todifferent herbicides, the progeny plants will have the combinedherbicide tolerance characteristics of the first and second plants. Themethods of the invention can further involve one or more generations ofbackcrossing the progeny plants of the first cross to a plant of thesame line or genotype as either the first or second plant.Alternatively, the progeny of the first cross or any subsequent crosscan be crossed to a third plant that is of a different line or genotypethan either the first or second plant. The present invention alsoprovides plants, plant organs, plant tissues, plant cells, seeds, andnon-human host cells that are transformed with the at least onepolynucleotide molecule, expression cassette, or transformation vectorof the invention. Such transformed plants, plant organs, plant tissues,plant cells, seeds, and non-human host cells have enhanced tolerance orresistance to at least one herbicide, at levels of the herbicide thatkill or inhibit the growth of an untransformed plant, plant tissue,plant cell, or non-human host cell, respectively. Preferably, thetransformed plants, plant tissues, plant cells, and seeds of theinvention are Arabidopsis thaliana and crop plants.

It is to be understood that the plant of the present invention cancomprise a wild type PPO nucleic acid in addition to a mut-PPO nucleicacid. It is contemplated that the benzoxazinone-derivative herbicidetolerant lines may contain a mutation in only one of multiple PPOisoenzymes. Therefore, the present invention includes a plant comprisingone or more mut-PPO nucleic acids in addition to one or more wild typePPO nucleic acids.

In another embodiment, the invention refers to a seed produced by atransgenic plant comprising a plant cell of the present invention,wherein the seed is true breeding for an increased resistance to abenzoxazinone-derivative herbicide as compared to a wild type variety ofthe seed.

In another embodiment, the invention refers to a method of producing atransgenic plant cell with an increased resistance to abenzoxazinone-derivative herbicide as compared to a wild type variety ofthe plant cell comprising, transforming the plant cell with anexpression cassette comprising a mut-PPO nucleic acid.

In another embodiment, the invention refers to a method of producing atransgenic plant comprising, (a) transforming a plant cell with anexpression cassette comprising a mut-PPO nucleic acid, and (b)generating a plant with an increased resistance tobenzoxazinone-derivative herbicide from the plant cell.

Consequently, mut-PPO nucleic acids of the invention are provided inexpression cassettes for expression in the plant of interest. Thecassette will include regulatory sequences operably linked to a mut-PPOnucleic acid sequence of the invention. The term “regulatory element” asused herein refers to a polynucleotide that is capable of regulating thetranscription of an operably linked polynucleotide. It includes, but notlimited to, promoters, enhancers, introns, 5′ UTRs, and 3′ UTRs. By“operably linked” is intended a functional linkage between a promoterand a second sequence, wherein the promoter sequence initiates andmediates transcription of the DNA sequence corresponding to the secondsequence. Generally, operably linked means that the nucleic acidsequences being linked are contiguous and, where necessary to join twoprotein coding regions, contiguous and in the same reading frame. Thecassette may additionally contain at least one additional gene to becotransformed into the organism. Alternatively, the additional gene(s)can be provided on multiple expression cassettes.

Such an expression cassette is provided with a plurality of restrictionsites for insertion of the mut-PPO nucleic acid sequence to be under thetranscriptional regulation of the regulatory regions. The expressioncassette may additionally contain selectable marker genes.

The expression cassette will include in the 5′-3′ direction oftranscription, a transcriptional and translational initiation region(i.e., a promoter), a mut-PPO nucleic acid sequence of the invention,and a transcriptional and translational termination region (i.e.,termination region) functional in plants. The promoter may be native oranalogous, or foreign or heterologous, to the plant host and/or to themut-PPO nucleic acid sequence of the invention. Additionally, thepromoter may be the natural sequence or alternatively a syntheticsequence. Where the promoter is “foreign” or “heterologous” to the planthost, it is intended that the promoter is not found in the native plantinto which the promoter is introduced. Where the promoter is “foreign”or “heterologous” to the mut-PPO nucleic acid sequence of the invention,it is intended that the promoter is not the native or naturallyoccurring promoter for the operably linked mut-PPO nucleic acid sequenceof the invention. As used herein, a chimeric gene comprises a codingsequence operably linked to a transcription initiation region that isheterologous to the coding sequence.

While it may be preferable to express the mut-PPO nucleic acids of theinvention using heterologous promoters, the native promoter sequencesmay be used. Such constructs would change expression levels of themut-PPO protein in the plant or plant cell. Thus, the phenotype of theplant or plant cell is altered.

The termination region may be native with the transcriptional initiationregion, may be native with the operably linked mut-PPO sequence ofinterest, may be native with the plant host, or may be derived fromanother source (i.e., foreign or heterologous to the promoter, themut-PPO nucleic acid sequence of interest, the plant host, or anycombination thereof). Convenient termination regions are available fromthe Ti-plasmid of A. tumefaciens, such as the octopine synthase andnopaline synthase termination regions. See also Guerineau et al. (1991)Mol. Gen. Genet. 262: 141-144; Proudfoot (1991) Cell 64:671-674;Sanfacon et al. (1991) Genes Dev. 5: 141-149; Mogen et al. (1990) PlantCell 2: 1261-1272; Munroe et al. (1990) Gene 91: 151-158; Ballast al.(1989) Nucleic Acids Res. 17:7891-7903; and Joshi et al. (1987) NucleicAcid Res. 15:9627-9639. Where appropriate, the gene(s) may be optimizedfor increased expression in the transformed plant. That is, the genescan be synthesized using plant-preferred codons for improved expression.See, for example, Campbell and Gowri (1990) Plant Physiol. 92: 1-11 fora discussion of host-preferred codon usage. Methods are available in theart for synthesizing plant-preferred genes. See, for example, U.S. Pat.Nos. 5,380,831, and 5,436,391, and Murray et al. (1989) Nucleic AcidsRes. 17:477-498, herein incorporated by reference.

Additional sequence modifications are known to enhance gene expressionin a cellular host. These include elimination of sequences encodingspurious polyadenylation signals, exon-intron splice site signals,transposon-like repeats, and other such well-characterized sequencesthat may be deleterious to gene expression. The G-C content of thesequence may be adjusted to levels average for a given cellular host, ascalculated by reference to known genes expressed in the host cell. Whenpossible, the sequence is modified to avoid predicted hairpin secondarymRNA structures. Nucleotide sequences for enhancing gene expression canalso be used in the plant expression vectors. These include the intronsof the maize Adhl, intronl gene (Callis et al. Genes and Development 1:1183-1200, 1987), and leader sequences, (W-sequence) from the TobaccoMosaic virus (TMV), Maize Chlorotic Mottle Virus and Alfalfa MosaicVirus (Gallie et al. Nucleic Acid Res. 15:8693-8711, 1987 and Skuzeskiet al. Plant Mol. Biol. 15:65-79, 1990). The first intron from theshrunken-1 locus of maize, has been shown to increase expression ofgenes in chimeric gene constructs. U.S. Pat. Nos. 5,424,412 and5,593,874 disclose the use of specific introns in gene expressionconstructs, and Gallie et al. (Plant Physiol. 106:929-939, 1994) alsohave shown that introns are useful for regulating gene expression on atissue specific basis. To further enhance or to optimize mut-PPO geneexpression, the plant expression vectors of the invention may alsocontain DNA sequences containing matrix attachment regions (MARs). Plantcells transformed with such modified expression systems, then, mayexhibit overexpression or constitutive expression of a nucleotidesequence of the invention.

The expression cassettes may additionally contain 5′ leader sequences inthe expression cassette construct. Such leader sequences can act toenhance translation. Translation leaders are known in the art andinclude: picornavirus leaders, for example, EMCV leader(Encephalomyocarditis 5′ noncoding region) (Elroy-Stein et al. (1989)Proc. Natl. Acad. ScL USA 86:6126-6130); potyvirus leaders, for example,TEV leader (Tobacco Etch Virus) (Gallie et al. (1995) Gene165(2):233-238), MDMV leader (Maize Dwarf Mosaic Virus) (Virology154:9-20), and human immunoglobulin heavy-chain binding protein (BiP)(Macejak et al. (1991) Nature 353:90-94); untranslated leader from thecoat protein mRNA of alfalfa mosaic virus (AMV RNA 4) (Jobling et al.(1987) Nature 325:622-625); tobacco mosaic virus leader (TMV) (Gallie etal. (1989) in Molecular Biology of RNA, ed. Cech (Liss, New York), pp.237-256); and maize chlorotic mottle virus leader (MCMV) (Lommel et al.(1991) Virology 81:382-385). See also, Della-Cioppa et al. (1987) PlantPhysiol. 84:965-968. Other methods known to enhance translation can alsobe utilized, for example, introns, and the like.

In preparing the expression cassette, the various DNA fragments may bemanipulated, so as to provide for the DNA sequences in the properorientation and, as appropriate, in the proper reading frame. Towardthis end, adapters or linkers may be employed to join the DNA fragmentsor other manipulations may be involved to provide for convenientrestriction sites, removal of superfluous DNA, removal of restrictionsites, or the like. For this purpose, in vitro mutagenesis, primerrepair, restriction, annealing, resubstitutions, e.g., transitions andtrans versions, may be involved.

A number of promoters can be used in the practice of the invention. Thepromoters can be selected based on the desired outcome. The nucleicacids can be combined with constitutive, tissue-preferred, or otherpromoters for expression in plants. Such constitutive promoters include,for example, the core promoter of the Rsyn7 promoter and otherconstitutive promoters disclosed in WO 99/43838 and U.S. Pat. No.6,072,050; the core CaMV 35S promoter (Odell et al. (1985) Nature313:810-812); rice actin (McElroy et al. (1990) Plant Cell 2: 163-171);ubiquitin (Christensen et al. (1989) Plant Mol. Biol. 12:619-632 andChristensen et al. (1992) Plant Mol. Biol. 18:675-689); pEMU (Last etal. (1991) Theor. Appl. Genet. 81:581-588); MAS (Velten et al. (1984)EMBO J. 3:2723-2730); ALS promoter (U.S. Pat. No. 5,659,026), and thelike. Other constitutive promoters include, for example, U.S. Pat. Nos.5,608,149; 5,608,144; 5,604,121; 5,569,597; 5,466,785; 5,399,680;5,268,463; 5,608,142; and 6,177,611.

Tissue-preferred promoters can be utilized to target enhanced mut-PPOexpression within a particular plant tissue. Such tissue-preferredpromoters include, but are not limited to, leaf-preferred promoters,root-preferred promoters, seed-preferred promoters, and stem-preferredpromoters. Tissue-preferred promoters include Yamamoto et al. (1997)Plant J. 12(2):255-265; Kawamata et al. (1997) Plant Cell Physiol.38(7):792-803; Hansen et al. (1997) Mol. Gen Genet. 254(3):337-343;Russell et al. (1997) Transgenic Res. 6(2): 157-168; Rinehart et al.(1996) Plant Physiol. 112(3): 1331-1341; Van Camp et al. (1996) PlantPhysiol. 112(2):525-535; Canevascini et al. (1996) Plant Physiol.112(2):513-524; Yamamoto et al. (1994) Plant Cell Physiol.35(5):773-778; Lam (1994) Results Probl. Cell Differ. 20: 181-196;Orozco et al. (1993) Plant Mol Biol. 23(6): 1129-1138; Matsuokae/[alpha]/. (1993) Proc Natl. Acad. Sci. USA 90(20):9586-9590; andGuevara-Garcia et al. (1993) Plant J. 4(3):495-505. Such promoters canbe modified, if necessary, for weak expression. In one embodiment, thenucleic acids of interest are targeted to the chloroplast forexpression. In this manner, where the nucleic acid of interest is notdirectly inserted into the chloroplast, the expression cassette willadditionally contain a chloroplast-targeting sequence comprising anucleotide sequence that encodes a chloroplast transit peptide to directthe gene product of interest to the chloroplasts. Such transit peptidesare known in the art. With respect to chloroplast-targeting sequences,“operably linked” means that the nucleic acid sequence encoding atransit peptide (i.e., the chloroplast-targeting sequence) is linked tothe mut-PPO nucleic acid of the invention such that the two sequencesare contiguous and in the same reading frame. See, for example, VonHeijne et al. (1991) Plant Mol. Biol. Rep. 9: 104-126; Clark et al.(1989) J. Biol. Chem. 264:17544-17550; Della-Cioppa et al. (1987) PlantPhysiol. 84:965-968; Romer et al. (1993) Biochem. Biophys. Res. Commun.196:1414-1421; and Shah et al. (1986) Science 233:478-481. While themut-PPO proteins of the invention include a native chloroplast transitpeptide, any chloroplast transit peptide known in the art can be fusedto the amino acid sequence of a mature mut-PPO protein of the inventionby operably linking a choloroplast-targeting sequence to the 5′-end of anucleotide sequence encoding a mature mut-PPO protein of the invention.Chloroplast targeting sequences are known in the art and include thechloroplast small subunit of ribulose-1,5-bisphosphate carboxylase(Rubisco) (de Castro Silva Filho et al. (1996) Plant Mol. Biol.30:769-780; Schnell et al. (1991) J. Biol. Chem. 266(5):3335-3342);5-(enolpyruvyl)shikimate-3-phosphate synthase (EPSPS) (Archer et al.(1990) J. Bioenerg. Biomemb. 22(6):789-810); tryptophan synthase (Zhaoet al. (1995) J. Biol. Chem. 270(11):6081-6087); plastocyanin (Lawrenceet al. (1997) J. Biol. Chem. 272(33):20357-20363); chorismate synthase(Schmidt et al. (1993) J. Biol. Chem. 268(36):27447-27457); and thelight harvesting chlorophyll a/b binding protein (LHBP) (Lamppa et al.(1988) J. Biol. Chem. 263: 14996-14999). See also Von Heijne et al.(1991) Plant Mol. Biol. Rep. 9: 104-126; Clark et al. (1989) J. Biol.Chem. 264:17544-17550; Della-Cioppa et al. (1987) Plant Physiol.84:965-968; Romer et al. (1993) Biochem. Biophys. Res. Commun. 196:1414-1421; and Shah et al. (1986) Science 233:478-481.

Methods for transformation of chloroplasts are known in the art. See,for example, Svab et al. (1990) Proc. Natl. Acad. ScL USA 87:8526-8530;Svab and Maliga (1993) Proc. Natl. Acad. Sci. USA 90:913-917; Svab andMaliga (1993) EMBO J. 12:601-606. The method relies on particle gundelivery of DNA containing a selectable marker and targeting of the DNAto the plastid genome through homologous recombination. Additionally,plastid transformation can be accomplished by transactivation of asilent plastid-borne transgene by tissue-preferred expression of anuclear-encoded and plastid-directed RNA polymerase. Such a system hasbeen reported in McBride et al. (1994) Proc. Natl. Acad. Sci. USA91:7301-7305. The nucleic acids of interest to be targeted to thechloroplast may be optimized for expression in the chloroplast toaccount for differences in codon usage between the plant nucleus andthis organelle. In this manner, the nucleic acids of interest may besynthesized using chloroplast-preferred codons. See, for example, U.S.Pat. No. 5,380,831, herein incorporated by reference.

In a preferred embodiment, the mut-PPO nucleic acid comprises apolynucleotide sequence selected from the group consisting of: a) apolynucleotide as shown in SEQ ID NO: 1, 3, 5, 7, 9, 11, 13, 15, 17, 19,21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, or 45, or a variant orderivative thereof; b) a polynucleotide encoding a polypeptide as shownin SEQ ID NO: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30,32, 34, 36, 38, 40, 42, 44, or 46, or a variant or derivative thereof;c) a polynucleotide comprising at least 60 consecutive nucleotides ofany of a) or c); and d) a polynucleotide complementary to thepolynucleotide of any of a) through c)

Preferably, the expression cassette further comprises a transcriptioninitiation regulatory region and a translation initiation regulatoryregion that are functional in the plant.

While the polynucleotides of the invention find use as selectable markergenes for plant transformation, the expression cassettes of theinvention can include another selectable marker gene for the selectionof transformed cells. Selectable marker genes, including those of thepresent invention, are utilized for the selection of transformed cellsor tissues. Marker genes include, but are not limited to, genes encodingantibiotic resistance, such as those encoding neomycinphosphotransferase II (NEO) and hygromycin phosphotransferase (HPT), aswell as genes conferring resistance to herbicidal compounds, such asglufosinate ammonium, bromoxynil, imidazolinones, and2,4-dichlorophenoxyacetate (2,4-D). See generally, Yarranton (1992)Curr. Opin. Biotech. 3:506-511; Christophers on et al (1992) Proc. Natl.Acad. ScL USA 89:6314-6318; Yao et al. (1992) Cell 71:63-72; Reznikoff(1992) Mol Microbiol 6:2419-2422; Barkley et al (1980) in The Operon,pp. 177-220; Hu et al (1987) Cell 48:555-566; Brown et al (1987) Cell49:603-612; Figge et al (1988) Cell 52:713-722; Deuschle et al (1989)Proc. Natl Acad. AcL USA 86:5400-5404; Fuerst et al (1989) Proc. NatlAcad. ScL USA 86:2549-2553; Deuschle et al (1990) Science 248:480-483;Gossen (1993) Ph.D. Thesis, University of Heidelberg; Reines et al(1993) Proc. Natl Acad. ScL USA 90: 1917-1921; Labow et al (1990) MolCell Biol 10:3343-3356; Zambretti et al (1992) Proc. Natl Acad. ScL USA89:3952-3956; Bairn et al (1991) Proc. Natl Acad. ScL USA 88:5072-5076;Wyborski et al (1991) Nucleic Acids Res. 19:4647-4653; Hillenand-Wissman(1989) Topics Mol Struc. Biol 10: 143-162; Degenkolb et al (1991)Antimicrob. Agents Chemother. 35: 1591-1595; Kleinschnidt et al (1988)Biochemistry 27: 1094-1104; Bonin (1993) Ph.D. Thesis, University ofHeidelberg; Gossen et al (1992) Proc. Natl Acad. ScL USA 89:5547-5551;Oliva et al (1992) Antimicrob. Agents Chemother. 36:913-919; Hlavka etal (1985) Handbook of Experimental Pharmacology, Vol. 78(Springer-Verlag, Berlin); Gill et al (1988) Nature 334:721-724. Suchdisclosures are herein incorporated by reference. The above list ofselectable marker genes is not meant to be limiting. Any selectablemarker gene can be used in the present invention.

The invention further provides an isolated recombinant expression vectorcomprising the expression cassette containing a mut-PPO nucleic acid asdescribed above, wherein expression of the vector in a host cell resultsin increased tolerance to a benzoxazinone-derivative herbicide ascompared to a wild type variety of the host cell. As used herein, theterm “vector” refers to a nucleic acid molecule capable of transportinganother nucleic acid to which it has been linked. One type of vector isa “plasmid,” which refers to a circular double stranded DNA loop intowhich additional DNA segments can be ligated. Another type of vector isa viral vector, wherein additional DNA segments can be ligated into theviral genome. Certain vectors are capable of autonomous replication in ahost cell into which they are introduced (e.g., bacterial vectors havinga bacterial origin of replication and episomal mammalian vectors). Othervectors (e.g., non-episomal mammalian vectors) are integrated into thegenome of a host cell upon introduction into the host cell, and therebyare replicated along with the host genome. Moreover, certain vectors arecapable of directing the expression of genes to which they areoperatively linked. Such vectors are referred to herein as “expressionvectors.” In general, expression vectors of utility in recombinant DNAtechniques are often in the form of plasmids. In the presentspecification, “plasmid” and “vector” can be used interchangeably as theplasmid is the most commonly used form of vector. However, the inventionis intended to include such other forms of expression vectors, such asviral vectors (e.g., replication defective retroviruses, adenoviruses,and adeno-associated viruses), which serve equivalent functions.

The recombinant expression vectors of the invention comprise a nucleicacid of the invention in a form suitable for expression of the nucleicacid in a host cell, which means that the recombinant expression vectorsinclude one or more regulatory sequences, selected on the basis of thehost cells to be used for expression, which is operably linked to thenucleic acid sequence to be expressed. Regulatory sequences includethose that direct constitutive expression of a nucleotide sequence inmany types of host cells and those that direct expression of thenucleotide sequence only in certain host cells or under certainconditions. It will be appreciated by those skilled in the art that thedesign of the expression vector can depend on such factors as the choiceof the host cell to be transformed, the level of expression ofpolypeptide desired, etc. The expression vectors of the invention can beintroduced into host cells to thereby produce polypeptides or peptides,including fusion polypeptides or peptides, encoded by nucleic acids asdescribed herein (e.g., mut-PPO polypeptides, fusion polypeptides,etc.).

In a preferred embodiment of the present invention, the mut-PPOpolypeptides are expressed in plants and plants cells such asunicellular plant cells (such as algae) (See Falciatore et al., 1999,Marine Biotechnology 1(3):239-251 and references therein) and plantcells from higher plants (e.g., the spermatophytes, such as cropplants). A mut-PPO polynucleotide may be “introduced” into a plant cellby any means, including transfection, transformation or transduction,electroporation, particle bombardment, agroinfection, biolistics, andthe like. Suitable methods for transforming or transfecting host cellsincluding plant cells can be found in Sambrook et al. (MolecularCloning: A Laboratory Manual. 2nd, ed., Cold Spring Harbor Laboratory,Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., 1989) andother laboratory manuals such as Methods in Molecular Biology, 1995,Vol. 44, Agrobacterium protocols, ed: Gartland and Davey, Humana Press,Totowa, N.J. As increased tolerance to benzoxazinone-derivativeherbicides is a general trait wished to be inherited into a wide varietyof plants like maize, wheat, rye, oat, triticale, rice, barley, soybean,peanut, cotton, rapeseed and canola, manihot, pepper, sunflower andtagetes, solanaceous plants like potato, tobacco, eggplant, and tomato,Vicia species, pea, alfalfa, bushy plants (coffee, cacao, tea), Salixspecies, trees (oil palm, coconut), perennial grasses, and forage crops,these crop plants are also preferred target plants for a geneticengineering as one further embodiment of the present invention. In apreferred embodiment, the plant is a crop plant. Forage crops include,but are not limited to, Wheatgrass, Canarygrass, Bromegrass, WildryeGrass, Bluegrass, Orchardgrass, Alfalfa, Salfoin, Birdsfoot Trefoil,Alsike Clover, Red Clover, and Sweet Clover.

In one embodiment of the present invention, transfection of a mut-PPOpolynucleotide into a plant is achieved by Agrobacterium mediated genetransfer. One transformation method known to those of skill in the artis the dipping of a flowering plant into an Agrobacteria solution,wherein the Agrobacteria contains the mut-PPO nucleic acid, followed bybreeding of the transformed gametes. Agrobacterium mediated planttransformation can be performed using for example the GV3101(pMP90)(Koncz and Schell, 1986, Mol. Gen. Genet. 204:383-396) or LBA4404(Clontech) Agrobacterium tumefaciens strain. Transformation can beperformed by standard transformation and regeneration techniques(Deblaere et al., 1994, Nucl. Acids. Res. 13:4777-4788; Gelvin, StantonB. and Schilperoort, Robert A, Plant Molecular Biology Manual, 2ndEd.-Dordrecht: Kluwer Academic Publ., 1995.—in Sect., Ringbuc ZentraleSignatur: BT11-P ISBN 0-7923-2731-4; Glick, Bernard R. and Thompson,John E., Methods in Plant Molecular Biology and Biotechnology, BocaRaton:CRC Press, 1993 360 S., ISBN 0-8493-5164-2). For example, rapeseedcan be transformed via cotyledon or hypocotyl transformation (Moloney etal., 1989, Plant Cell Report 8:238-242; De Block et al., 1989, PlantPhysiol. 91:694-701). Use of antibiotics for Agrobacterium and plantselection depends on the binary vector and the Agrobacterium strain usedfor transformation. Rapeseed selection is normally performed usingkanamycin as selectable plant marker. Agrobacterium mediated genetransfer to flax can be performed using, for example, a techniquedescribed by Mlynarova et al., 1994, Plant Cell Report 13:282-285.Additionally, transformation of soybean can be performed using forexample a technique described in European Patent No. 0424 047, U.S. Pat.No. 5,322,783, European Patent No. 0397 687, U.S. Pat. No. 5,376,543, orU.S. Pat. No. 5,169,770. Transformation of maize can be achieved byparticle bombardment, polyethylene glycol mediated DNA uptake, or viathe silicon carbide fiber technique. (See, for example, Freeling andWalbot “The maize handbook” Springer Verlag: N.Y. (1993) ISBN3-540-97826-7). A specific example of maize transformation is found inU.S. Pat. No. 5,990,387, and a specific example of wheat transformationcan be found in PCT Application No. WO 93/07256.

According to the present invention, the introduced mut-PPOpolynucleotide may be maintained in the plant cell stably if it isincorporated into a non-chromosomal autonomous replicon or integratedinto the plant chromosomes. Alternatively, the introduced mut-PPOpolynucleotide may be present on an extra-chromosomal non-replicatingvector and be transiently expressed or transiently active. In oneembodiment, a homologous recombinant microorganism can be createdwherein the mut-PPO polynucleotide is integrated into a chromosome, avector is prepared which contains at least a portion of an PPO gene intowhich a deletion, addition, or substitution has been introduced tothereby alter, e.g., functionally disrupt, the endogenous PPO gene andto create a mut-PPO gene. To create a point mutation via homologousrecombination, DNA-RNA hybrids can be used in a technique known aschimeraplasty (Cole-Strauss et al., 1999, Nucleic Acids Research27(5):1323-1330 and Kmiec, 1999, Gene therapy American Scientist87(3):240-247). Other homologous recombination procedures in Triticumspecies are also well known in the art and are contemplated for useherein.

In the homologous recombination vector, the mut-PPO gene can be flankedat its 5′ and 3′ ends by an additional nucleic acid molecule of the PPOgene to allow for homologous recombination to occur between theexogenous mut-PPO gene carried by the vector and an endogenous PPO gene,in a microorganism or plant. The additional flanking PPO nucleic acidmolecule is of sufficient length for successful homologous recombinationwith the endogenous gene. Typically, several hundreds of base pairs upto kilobases of flanking DNA (both at the 5′ and 3′ ends) are includedin the vector (see e.g., Thomas, K. R., and Capecchi, M. R., 1987, Cell51:503 for a description of homologous recombination vectors or Streppet al., 1998, PNAS, 95(8):4368-4373 for cDNA based recombination inPhyscomitrella patens). However, since the mut-PPO gene normally differsfrom the PPO gene at very few amino acids, a flanking sequence is notalways necessary. The homologous recombination vector is introduced intoa microorganism or plant cell (e.g., via polyethylene glycol mediatedDNA), and cells in which the introduced mut-PPO gene has homologouslyrecombined with the endogenous PPO gene are selected using art-knowntechniques.

In another embodiment, recombinant microorganisms can be produced thatcontain selected systems that allow for regulated expression of theintroduced gene. For example, inclusion of a mut-PPO gene on a vectorplacing it under control of the lac operon permits expression of themut-PPO gene only in the presence of IPTG. Such regulatory systems arewell known in the art.

Another aspect of the invention pertains to host cells into which arecombinant expression vector of the invention has been introduced. Theterms “host cell” and “recombinant host cell” are used interchangeablyherein. It is understood that such terms refer not only to theparticular subject cell but they also apply to the progeny or potentialprogeny of such a cell. Because certain modifications may occur insucceeding generations due to either mutation or environmentalinfluences, such progeny may not, in fact, be identical to the parentcell, but are still included within the scope of the term as usedherein. A host cell can be any prokaryotic or eukaryotic cell. Forexample, a mut-PPO polynucleotide can be expressed in bacterial cellssuch as C. glutamicum, insect cells, fungal cells, or mammalian cells(such as Chinese hamster ovary cells (CHO) or COS cells), algae,ciliates, plant cells, fungi or other microorganisms like C. glutamicum.Other suitable host cells are known to those skilled in the art.

A host cell of the invention, such as a prokaryotic or eukaryotic hostcell in culture, can be used to produce (i.e., express) a mut-PPOpolynucleotide. Accordingly, the invention further provides methods forproducing mut-PPO polypeptides using the host cells of the invention. Inone embodiment, the method comprises culturing the host cell ofinvention (into which a recombinant expression vector encoding a mut-PPOpolypeptide has been introduced, or into which genome has beenintroduced a gene encoding a wild-type or mut-PPO polypeptide) in asuitable medium until mut-PPO polypeptide is produced. In anotherembodiment, the method further comprises isolating mut-PPO polypeptidesfrom the medium or the host cell. Another aspect of the inventionpertains to isolated mut-PPO polypeptides, and biologically activeportions thereof. An “isolated” or “purified” polypeptide orbiologically active portion thereof is free of some of the cellularmaterial when produced by recombinant DNA techniques, or chemicalprecursors or other chemicals when chemically synthesized. The language“substantially free of cellular material” includes preparations ofmut-PPO polypeptide in which the polypeptide is separated from some ofthe cellular components of the cells in which it is naturally orrecombinantly produced. In one embodiment, the language “substantiallyfree of cellular material” includes preparations of a mut-PPOpolypeptide having less than about 30% (by dry weight) of non-mut-PPOmaterial (also referred to herein as a “contaminating polypeptide”),more preferably less than about 20% of non-mut-PPO material, still morepreferably less than about 10% of non-mut-PPO material, and mostpreferably less than about 5% non-mut-PPO material.

When the mut-PPO polypeptide, or biologically active portion thereof, isrecombinantly produced, it is also preferably substantially free ofculture medium, i.e., culture medium represents less than about 20%,more preferably less than about 10%, and most preferably less than about5% of the volume of the polypeptide preparation. The language“substantially free of chemical precursors or other chemicals” includespreparations of mut-PPO polypeptide in which the polypeptide isseparated from chemical precursors or other chemicals that are involvedin the synthesis of the polypeptide. In one embodiment, the language“substantially free of chemical precursors or other chemicals” includespreparations of a mut-PPO polypeptide having less than about 30% (by dryweight) of chemical precursors or non-mut-PPO chemicals, more preferablyless than about 20% chemical precursors or non-mut-PPO chemicals, stillmore preferably less than about 10% chemical precursors or non-mut-PPOchemicals, and most preferably less than about 5% chemical precursors ornon-mut-PPO chemicals. In preferred embodiments, isolated polypeptides,or biologically active portions thereof, lack contaminating polypeptidesfrom the same organism from which the mut-PPO polypeptide is derived.Typically, such polypeptides are produced by recombinant expression of,for example, a mut-PPO polypeptide in plants other than, or inmicroorganisms such as C. glutamicum, ciliates, algae, or fungi.

As described above, the present invention teaches compositions andmethods for increasing the benzoxazinone-derivative tolerance of a cropplant or seed as compared to a wild-type variety of the plant or seed.In a preferred embodiment, the benzoxazinone-derivative tolerance of acrop plant or seed is increased such that the plant or seed canwithstand a benzoxazinone-derivative herbicide application of preferablyapproximately 1-1000 g ai ha⁻¹, more preferably 20-160 g ai ha⁻¹, andmost preferably 40-80 g ai ha⁻¹. As used herein, to “withstand” abenzoxazinone-derivative herbicide application means that the plant iseither not killed or not injured by such application.

Furthermore, the present invention provides methods that involve the useof at least one benzoxazinone-derivative herbicide as described indetail supra.

In these methods, the benzoxazinone-derivative herbicide can be appliedby any method known in the art including, but not limited to, seedtreatment, soil treatment, and foliar treatment. Prior to application,the benzoxazinone-derivative herbicide can be converted into thecustomary formulations, for example solutions, emulsions, suspensions,dusts, powders, pastes and granules. The use form depends on theparticular intended purpose; in each case, it should ensure a fine andeven distribution of the compound according to the invention.

By providing plants having increased tolerance tobenzoxazinone-derivative herbicide, a wide variety of formulations canbe employed for protecting plants from weeds, so as to enhance plantgrowth and reduce competition for nutrients. A benzoxazinone-derivativeherbicide can be used by itself for pre-emergence, post-emergence,pre-planting, and at-planting control of weeds in areas surrounding thecrop plants described herein, or a benzoxazinone-derivative herbicideformulation can be used that contains other additives. Thebenzoxazinone-derivative herbicide can also be used as a seed treatment.Additives found in a benzoxazinone-derivative herbicide formulationinclude other herbicides, detergents, adjuvants, spreading agents,sticking agents, stabilizing agents, or the like. Thebenzoxazinone-derivative herbicide formulation can be a wet or drypreparation and can include, but is not limited to, flowable powders,emulsifiable concentrates, and liquid concentrates. Thebenzoxazinone-derivative herbicide and herbicide formulations can beapplied in accordance with conventional methods, for example, byspraying, irrigation, dusting, or the like.

Suitable formulations are describe in detail in PCT/EP2009/063387 andPCT/EP2009/063386, which are incorporated herein by reference.

It should also be understood that the foregoing relates to preferredembodiments of the present invention and that numerous changes may bemade therein without departing from the scope of the invention. Theinvention is further illustrated by the following examples, which arenot to be construed in any way as imposing limitations upon the scopethereof. On the contrary, it is to be clearly understood that resort maybe had to various other embodiments, modifications, and equivalentsthereof, which, after reading the description herein, may suggestthemselves to those skilled in the art without departing from the spiritof the present invention and/or the scope of the appended claims.

EXAMPLES Example 1: Site-Directed Mutagenesis of Amaranthus PPO

Cloning of Aramanthus PPO

The Amaranthus tuberculatus coding sequence for PPO-susceptible and-resistant isoforms, and all mutant combinations and multiple mutations,(SEQ ID No: 1, 3, 5, 7) were synthesized and cloned by Geneart (GeneartAG, Regensburg, Germany).

Plasmids were isolated from E. coli TOP10 by performing a plasmidminpreparation and confirmed by DNA sequencing.

Expression and Purification of Recombinant Wildtype and Mutant PPO

(Taken from: Franck E. Dayan, Pankaj R. Daga, Stephen O. Duke, Ryan M.Lee, Patrick J. Tranel, Robert J. Doerksen. Biochemical and structuralconsequences of a glycine deletion in the α-8 helix ofprotoporphyrinogen oxidase. Biochimica et Biophysica Acta 1804 (2010),1548-56)

Clones in pRSET vector were transformed into BL21(DE3)-pLysS strain ofE. coli. Cells were grown in 250 mL of LB with 100 μgmL-1 ofcarbenicillin, shaking overnight at 37° C. Cultures were diluted in 1 Lof LB with antibiotic and grown at 37° C. shaking for 2 h, induced with1 mM IPTG and grown at 25° C. shaking for 5 more hours. The cells wereharvested by centrifugation at 1600×g, washed with 0.09% NaCl, andstored at −80° C.

Cells were lysed using a French press at 140 MPa in 50 mM sodiumphosphate pH 7.5, 1 M NaCl, 5 mM imidazole, 5% glycerol, and 1 μg mL-1leupeptin. Following lysis, 0.5 U of benzonase (Novagen, EMD Chemicals,Inc., Gibbstown, N.J.) and PMSF (final concentration of 1 mM) wereadded. Cell debris was removed by centrifugation at 3000×g. His-taggedPPO proteins were purified on a nickel activated Hitrap Chelating HPcolumn (GE Healthcare Bio-Sciences Corp., Piscataway, N.J.) equilibratedwith 20 mM sodium phosphate pH 8.0, 50 mM NaCl, 5 mM imidazole, 5 mMMgCl2, 0.1 mM EDTA, and 17% glycerol.

PPO elutedwith 250 mMimidazole. The active proteinwas desalted on aPD-10 column (GE Healthcare Bio-Sciences Corp., Piscataway, N.J.)equilibrated with a 20 mM sodium phosphate buffer, pH 7.5, 5 mM MgCl2, 1mM EDTA and 17% glycerol. Each liter of culture provided approximately10 mg of pure PPO, which was stored at −20° C. until being used inassays.

PPO Activity Assay

PPO Enzyme Assay (Non-Recombinant). PPO protein (EC 1.3.3.4) wasextracted from coleoptiles or shoots (150 g fresh weight) of dark-growncorn, black nightshade, morning glory, and velvetleaf seedlings asdescribed previously (Grossmann et al. 2010). Before harvesting, theseedlings were allowed to green for 2 hours in the light in order toachieve the highest specific enzyme activities in the thylakoidfractions at low chlorophyll concentrations. At high chlorophyllconcentrations significant quenching of fluorescence occurs, whichlimits the amount of green thylakoids that can be used in the test.Plant materials were homogenized in the cold with a Braun blender usinga fresh-weight-to-volume ratio of 1:4. Homogenization buffer consistedof tris(hydroxymethyl)aminomethane (Tris)-HCl (50 mM; pH 7.3), sucrose(0.5 M), magnesium chloride (1 mM), ethylenediaminetetraacetic acid(EDTA) (1 mM) and bovine serum albumin (2 g L⁻¹). After filtrationthrough four layers of Miracloth, crude plastid preparations wereobtained after centrifugation at 10 000×g for 5 min and resuspension inhomogenization buffer before centrifugation at 150×g for 2 min to removecrude cell debris. The supernatant was centrifuged at 4000×g for 15 minand the pellet fraction was resuspended in 1 ml of a buffer containingTris-HCl (50 mM; pH 7.3), EDTA (2 mM), leupeptin (2 μM), pepstatin (2μM) and glycerol (200 ml L⁻¹) and stored at −80° C. until use. Proteinwas determined in the enzyme extract with bovine serum albumin as astandard. PPO activity was assayed fluorometrically by monitoring therate of Proto formation from chemically reduced protoporphyrinogen IXunder initial velocity conditions. The assay mixture consisted ofTris-HCl (100 mM; pH 7.3), EDTA (1 mM), dithiothreitol (5 mM), Tween 80(0.085%), protoporphyrinogen IX (2 μM), and 40 μg extracted protein in atotal volume of 200 μl. The reaction was initiated by addition ofsubstrate protoporphyrinogen IX at 22° C. saflufenacil,benzoxazinone-derivative herbicide, flumioxazin, butafenacil,acifluorfen, lactofen, bifenox, diuron, sulfentrazone were prepared indimethyl sulfoxide (DMSO) solution (0.1 mM concentration of DMSO in theassay) and added to the assay mixture in concentrations of 0.005 pM to 5μM before incubation. Fluorescence was monitored directly from the assaymixture using a POLARstar Optima/Galaxy (BMG) with excitation at 405 nmand emission monitored at 630 nm. Non-enzymatic activity in the presenceof heat-inactivated extract was negligible. Inhibition of enzymeactivity induced by the herbicide was expressed as percentage inhibitionrelative to untreated controls. Molar concentrations of compoundrequired for 50% enzyme inhibition (IC₅₀ values) were calculated byfitting the values to the dose-response equation using non-linearregression analysis.

PPO Enzyme Assay (Recombinant). Proto was purchased from Sigma-Aldrich(Milwaukee,Wis.). Protogen was prepared according to Jacobs and Jacobs(N. J. Jacobs, J. M. Jacobs, Assay for enzymatic protoporphyrinogenoxidation, a late step in heme synthesis, Enzyme 28 (1982) 206-219).Assays were conducted in 100 mM sodium phosphate pH 7.4 with 0.1 mMEDTA, 0.1% Tween 20, 5 μM FAD, and 500 mM imidazole. Dose—responsecurves with the PPO inhibitors saflufenacil, benzoxazinone-derivativeherbicide, flumioxazin, butafenacil, acifluorfen, lactofen, bifenox,diuron, sulfentrazone, and MC-15608 were obtained in the presence of 150μM Protogen. The excitation and emission bandwidths were set at 1.5 and30 nm, respectively. All assays were made in duplicates or triplicatesand measured using a POLARstar Optima/Galaxy (BMG) with excitation at405 nm and emission monitored at 630 nm. Molar concentrations ofcompound required for 50% enzyme inhibition (IC₅₀ values) werecalculated by fitting the values to the dose-response equation usingnon-linear regression analysis.

Example 2: Engineering PPO-Derivative Herbicide Tolerant Plants HavingWildtype or Mutated PPO Sequences

PPO-derivative herbicide tolerant soybean (Glycine max) or corn (Zeamays) plants are produced by a method as described by Olhoft et al. (USpatent 2009/0049567). For transformation of soybean or Arabidopsisthaliana, Wildtype or Mutated PPO sequences are cloned with standardcloning techniques as described in Sambrook et al. (Molecular cloning(2001) Cold Spring Harbor Laboratory Press) in a binary vectorcontaining resistance marker gene cassette (AHAS) and mutated PPOsequence (marked as GOI) in between ubiquitin promoter (PcUbi) andnopaline synthase terminator (NOS) sequence. For corn transformation,Wildtype or Mutated PPO sequences are cloned with standard cloningtechniques as described in Sambrook et al. (Molecular cloning (2001)Cold Spring Harbor Laboratory Press) in a binary vector containingresistance marker gene cassette (AHAS) and mutated PPO sequence (markedas GOI) in between corn ubiquitin promoter (ZmUbi) and nopaline synthaseterminator (NOS) sequence. Binary plasmids are introduced toAgrobacterium tumefaciens for plant transformation. Plasmid constructsare introduced into soybean's axillary meristem cells at the primarynode of seedling explants via Agrobacterium-mediated transformation.After inoculation and co-cultivation with Agrobacteria, the explants aretransferred to shoot introduction media without selection for one week.The explants were subsequently transferred to a shoot induction mediumwith 1-3 μM imazapyr (Arsenal) for 3 weeks to select for transformedcells. Explants with healthy callus/shoot pads at the primary node arethen transferred to shoot elongation medium containing 1-3 μM imazapyruntil a shoot elongated or the explant died. Transgenic plantlets arerooted, subjected to TaqMan analysis for the presence of the transgene,transferred to soil and grown to maturity in greenhouse. Transformationof corn plants are done by a method described by McElver and Singh (WO2008/124495). Plant transformation vector constructs containing mutatedPPO sequences are introduced into maize immature embryos viaAgrobacterium-mediated transformation.

Transformed cells were selected in selection media supplemented with0.5-1.5 μM imazethapyr for 3-4 weeks. Transgenic plantlets wereregenerated on plant regeneration media and rooted afterwards.Transgenic plantlets are subjected to TaqMan analysis for the presenceof the transgene before being transplanted to potting mixture and grownto maturity in greenhouse. Arabidopsis thaliana are transformed withwildtype or mutated PPO sequences by floral dip method as decribed byMcElver and Singh (WO 2008/124495). Transgenic Arabidopsis plants weresubjected to TaqMan analysis for analysis of the number of integrationloci. Transformation of Oryza sativa (rice) are done by protoplasttransformation as decribed by Peng et al. (U.S. Pat. No. 6,653,529) T0or T1 transgenic plant of soybean, corn, and rice containing mutated PPOsequences are tested for improved tolerance to PPO-derived herbicides ingreenhouse studies and mini-plot studies with the followingPPO-inhibiting herbicides: saflufenacil, benzoxazinone-derivativeherbicide, flumioxazin, butafenacil, acifluorfen, lactofen, bifenox,diuron, sulfentrazone.

Transgenic Arabidopsis thaliana plants were assayed for improvedtolerance to saflufenacil, benzoxazine-derivative herbicide,flumioxazin, butafenacil, acifluorfen, lactofen, bifenox, diuron,sulfentrazon in 48-well plates. Therefore, T2 seeds are surfacesterilized by stirring for 5 min in ethanol+water (70+30 by volume),rinsing one time with ethanol+water (70+30 by volume) and two times withsterile, deionized water. The seeds are resuspended in 0.1% agardissolved in water (w/v) Four to five seeds per well are plated on solidnutrient medium consisting of half-strength murashige skoog nutrientsolution, pH 5.8 (Murashige and Skoog (1962) Physiologia Plantarum 15:473-497). Compounds are dissolved in dimethylsulfoxid (DMSO) and addedto the medium prior solidification (final DMSO concentration 0.1%).Multi well plates are incubated in a growth chamber at 22° C., 75%relative humidity and 110 μmol Phot*m⁻²*s⁻¹ with 14:10 h light:darkphotoperiod. Growth inhibition is evaluated seven to ten days afterseeding in comparison to wild type plants. Additionally, transgenic T1Arabidopsis plants were tested for improved tolerance to PPO-inhibitingherbicides in greenhouse studies with the following PPO-inhibitingherbicides: saflufenacil, benzoxazinone.derivative herbicide,flumioxazin, butafenacil, acifluorfen, lactofen, bifenox, diuron,sulfentrazone.

Example 3: Tissue Culture Conditions

An in vitro tissue culture mutagenesis assay has been developed toisolate and characterize plant tissue (e.g., maize, rice tissue) that istolerant to protoporphyrinogen oxidase inhibiting herbicides,(saflufenacil, benzoxazinone-derivative herbicide, flumioxazin,butafenacil, acifluorfen, lactofen, bifenox, diuron, sulfentrazone). Theassay utilizes the somaclonal variation that is found in in vitro tissueculture. Spontaneous mutations derived from somaclonal variation can beenhanced by chemical mutagenesis and subsequent selection in a stepwisemanner, on increasing concentrations of herbicide.

The present invention provides tissue culture conditions for encouraginggrowth of friable, embryogenic maize or rice callus that is regenerable.Calli were initiated from 4 different maize or rice cultivarsencompassing Zea mays and Japonica (Taipei 309, Nipponbare, Koshihikari)and Indica (Indica 1) varieties, respectively. Seeds were surfacesterilized in 70% ethanol for approximately 1 min followed by 20%commercial Clorox bleach for 20 minutes. Seeds were rinsed with sterilewater and plated on callus induction media. Various callus inductionmedia were tested. The ingredient lists for the media tested arepresented in Table 4.

TABLE 4 Ingredient Supplier R001M R025M R026M R327M R008M MS711R B5Vitamins Sigma 1.0 X MS salts Sigma 1.0 X 1.0 X 1.0 X 1.0 X MS VitaminsSigma 1.0 X 1.0 X N6 salts Phytotech 4.0 g/L 4.0 g/L N6 vitaminsPhytotech 1.0 X 1.0 X L-Proline Sigma 2.9 g/L 0.5 g/L 1.2 g/L CasaminoAcids BD 0.3 g/L 0.3 g/L 2 g/L Casein Sigma 1.0 g/L Hydrolysate L-AspPhytotech 150 mg/L Monohydrate Nicotinic Acid Sigma 0.5 mg/L PyridoxineHCl Sigma 0.5 mg/L Thiamine HCl Sigma 1.0 mg/L Myo-inositol Sigma 100mg/L MES Sigma 500 mg/L 500 mg/L 500 mg/L 500 mg/L 500 mg/L 500 mg/LMaltose VWR 30 g/L 30 g/L 30 g/L 30 g/L Sorbitol Duchefa 30 g/L SucroseVWR 10 g/L 30 g/L NAA Duchefa 50 μg/L 2,4-D Sigma 2.0 mg/L 1.0 mg/LMgCl₂•6H₂O VWR 750 mg/L →pH 5.8 5.8 5.8 5.8 5.8 5.7 Gelrite Duchefa 4.0g/L 2.5 g/L Agarose Type1 Sigma 7.0 g/L 10 g/L 10 g/L →Autoclave 15 min15 min 15 min 15 min 15 min 20 min Kinetin Sigma 2.0 mg/L 2.0 mg/L NAADuchefa 1.0 mg/L 1.0 mg/L ABA Sigma 5.0 mg/L Cefotaxime Duchefa 0.1 g/L0.1 g/L 0.1 g/L Vancomycin Duchefa 0.1 g/L 0.1 g/L 0.1 g/L G418Disulfate Sigma 20 mg/L 20 mg/L 20 mg/L

R001M callus induction media was selected after testing numerousvariations. Cultures were kept in the dark at 30° C. Embryogenic calluswas subcultured to fresh media after 10-14 days.

Example 4: Selection of Herbicide-Tolerant Calli

Once tissue culture conditions were determined, further establishment ofselection conditions were established through the analysis of tissuesurvival in kill curves with saflufenacil, benzoxazinone-derivativeherbicide, flumioxazin, butafenacil, acifluorfen, lactofen, bifenox,diuron, sulfentrazone. Careful consideration of accumulation of theherbicide in the tissue, as well as its persistence and stability in thecells and the culture media was performed. Through these experiments, asub-lethal dose has been established for the initial selection ofmutated material.

After the establishment of the starting dose of saflufenacil,benzoxazinone-derivative herbicide, flumioxazin, butafenacil,acifluorfen, lactofen, bifenox, diuron, sulfentrazone in selectionmedia, the tissues were selected in a step-wise fashion by increasingthe concentration of the PPO inhibitor with each transfer until cellsare recovered that grew vigorously in the presence of toxic doses. Theresulting calli were further subcultured every 3-4 weeks to R001M withselective agent. Over 26,000 calli were subjected to selection for 4-5subcultures until the selective pressure was above toxic levels asdetermined by kill curves and observations of continued culture.

Alternatively, liquid cultures initiated from calli in MS711R with slowshaking and weekly subcultures. Once liquid cultures were established,selection agent was added directly to the flask at each subculture.Following 2-4 rounds of liquid selection, cultures were transferred tofilters on solid R001M media for further growth.

Example 5: Regeneration of Plants

Tolerant tissue was regenerated and characterized molecularly for PPOgene sequence mutations and/or biochemically for altered PPO activity inthe presence of the selective agent. In addition, genes involveddirectly and/or indirectly in tetrapyrrole biosynthesis and/ormetabolism pathways were also sequenced to characterize mutations.Finally, enzymes that change the fate (e.g. metabolism, translocation,transportaion) were also sequence to characterized mutations.

Following herbicide selection, calli were regenerated using a mediaregime of R025M for 10-14 days, R026M for ca. 2 weeks, R327M until wellformed shoots were developed, and R008S until shoots were well rootedfor transfer to the greenhouse. Regeneration was carried out in thelight. No selection agent was included during regeneration.

Once strong roots were established, M0 regenerants were transplant tothe greenhouse in square or round pots. Transplants were maintainedunder a clear plastic cup until they were adapted to greenhouseconditions. The greenhouse was set to a day/night cycle of 27° C./21° C.(80° F./70° F.) with 600 W high pressure sodium lights supplementinglight to maintain a 14 hour day length. Plants were watered according toneed, depending in the weather and fertilized daily.

Example 6: Sequence Analysis

Leaf tissue was collected from clonal plants separated for transplantingand analyzed as individuals. Genomic DNA was extracted using a Wizard®96 Magnetic DNA Plant System kit (Promega, U.S. Pat. Nos. 6,027,945 &6,368,800) as directed by the manufacturer. Isolated DNA was PCRamplified using the appropriate forward and reverse primer.

PCR amplification was performed using Hotstar Taq DNA Polymerase(Qiagen) using touchdown thermocycling program as follows: 96° C. for 15min, followed by 35 cycles (96° C., 30 sec; 58° C.-0.2° C. per cycle, 30sec; 72° C., 3 min and 30 sec), 10 min at 72° C.

PCR products were verified for concentration and fragment size viaagarose gel electrophoresis. Dephosphorylated PCR products were analyzedby direct sequence using the PCR primers (DNA Landmarks, or Entelechon).Chromatogram trace files (.scf) were analyzed for mutation relative tothe wild-type gene using Vector NTI Advance 10™ (Invitrogen). Based onsequence information, mutations were identified in several individuals.Sequence analysis was performed on the representative chromatograms andcorresponding AlignX alignment with default settings and edited to callsecondary peaks.

Example 7: Demonstration of Herbicide-Tolerance

Selected mutants and escapes were transferred to small pots. Wild-typecultivars were germinated from seed to serve as controls.

After ca. 3 weeks post-transplant, M0 regenerants were sprayed using atrack sprayer with saflufenacil, benzoxazinone-derivative herbicide,flumioxazin, butafenacil, acifluorfen, lactofen, bifenox, diuron,sulfentrazone supplemented with 0.1% methylated seed oil. After theplants had adapted to greenhouse conditions, a subset were sprayed withadditional saflufenacil or benzoxazinone-derivative herbicide. Oncesprayed, plants were kept on drought conditions for 24 hours beforebeing watered and fertilized again. Sprayed plants were photographed andrated for herbicide injury at 1 and 3 weeks after treatment. No injurywas observed on plants containing the heterozygous mutation whilecontrol plants and tissue culture escapes (regenerated plants negativefor the sequenced mutations) were heavily damaged after treatment.

Example 8: Herbicide Selection Using Tissue Culture

Media was selected for use and kill curves developed as specified above.For selection, different techniques were utilized. Either a step wiseselection was applied, or an immediate lethal level of herbicide wasapplied. In either case, all of the calli were transferred for each newround of selection. Selection was 4-5 cycles of culture with 3-5 weeksfor each cycle. Cali were placed onto nylon membranes to facilitatetransfer (200 micron pore sheets, Biodesign, Saco, Me.). Membranes werecut to fit 100×20 mm Petri dishes and were autoclaved prior to use 25-35calli (average weight/calli being 22 mg) were utilized in every plate.In addition, one set of calli were subjected to selection in liquidculture media with weekly subcultures followed by further selection onsemi-solid media.

Mutant lines were selected using saflufenacil, benzoxazinone-derivativeherbicide, flumioxazin, butafenacil, acifluorfen, lactofen, bifenox,diuron, sulfentrazone. Efficiencies of obtaining mutants was high eitherbased on a percentage of calli that gave rise to a regenerable, mutantline or the number of lines as determined by the gram of tissueutilized.

Example 9: Screening of Mutagenized Algae Cells to Identify HerbicideTolerant Clones and Identification of Causative Mutations in PPO Genes

To generate mutations in PPO genes conferring “PPO-inhibitingherbicides” resistance, screening with chemical or UV mutagenized cellpopulations can be used. Especially unicellular organisms likeChlamydomonas reinhardtii are useful for identifying dominant mutationsconferring herbicide resistance (Kataoka M, et al.; 1990; J. of Pest.Sci. 15: 449-451; Oshio H, et al.; 1993; Zeitschrift fur Naturforschung48: 339-344).

Algae cells of Chlamydomonas reinhardtii strains CC-503 and CC-1691(Duke University, Durham, USA) were propagated in TAP medium (Gorman andLevine; 1965; PNAS 54: 1665-1669) by constant shaking at 100 rpm, 22° C.and 30 μmol Phot*m⁻²*s⁻² light illumination. Compound screening wasperformed at 450 μmol Phot*m⁻²*s⁻² illumination. Sensitive strains ofChlamydomonas reinhardtii were mutagenized with 0.14 Methylmethanesulfonate (EMS) for 1 has described by Loppes (1969, Mol GenGenet 104: 172-177). Tolerant strains are identified by screening ofmutagenized cells on solid TAP medium plates containing “PPO-inhibitingherbicide” like saflufenacil or benzoxazinone-derivative herbicide atwildype-lethal concentrations depending on compound activity in CC-503or CC-1691 strain.

Standard techniques were used for isolation of RNA and cDNA synthesis asdescribed by Sambrock et al. (Molecular cloning (2001) Cold SpringHarbor Laboratory Press). Amplification of PPO genes from wild-type andresistant Chlamydomonas reinhardii from genomic DNA or copy DNA astemplate were performed by standard PCR techniques with DNAoligonucleotides as listed in Table 5. The resulting DNA molecules werecloned in standard sequencing vector (pJET1) and sequenced by standardsequencing techniques. Mutations were identified by comparing wildtypeand mutant PPO sequences by sequence alignment tool Align X (Vector NTIAdvance Software Version 10.3, Invitrogen, Carlsbad, Calif., USA).

TABLE 5 PCR primer for amplification of CrPPO Primer namePrimer sequence (5′-3′) Cr_PPO1_Fw ATGATGTTGACCCAGACTCCTGGGAC Cr_PPO1_RvTTAGGCCTTGACTGCGGCCTTGGAC

The invention claimed is:
 1. An isolated nucleic acid comprising anucleotide sequence encoding a mutated protoporphyrinogen oxidase(mut-PPO), wherein the encoded mut-PPO is a variant of SEQ ID NO: 46having at least 75% identity to SEQ ID NO: 46 and wherein the encodedmut-PPO comprises an amino acid substitution at a position correspondingto position Leu397 of SEQ ID NO:2 and an amino acid substitution at aposition corresponding to position Phe420 of SEQ ID NO:2, wherein theamino acid corresponding to position Leu397 of SEQ ID NO:2 issubstituted with aspartate, glutamate, or glutamine, and wherein theamino acid corresponding to position Phe420 of SEQ ID NO:2 issubstituted with valine or methionine.
 2. A plant or plant cellcomprising the nucleic acid of claim
 1. 3. A seed produced by the plantof claim 2, wherein the seed comprises the nucleic acid.
 4. The isolatednucleic acid of claim 1, wherein the encoded mut-PPO has at least 80%identity to SEQ ID NO: 46 and wherein the encoded mut-PPO comprises anamino acid substitution at a position corresponding to position Leu397of SEQ ID NO:2 and an amino acid substitution at a positioncorresponding to position Phe420 of SEQ ID NO:2, wherein the amino acidcorresponding to position Leu397 of SEQ ID NO:2 is substituted withaspartate, glutamate, or glutamine, and wherein the amino acidcorresponding to position Phe420 of SEQ ID NO:2 is substituted withvaline or methionine.
 5. The isolated nucleic acid of claim 1, whereinthe encoded mut-PPO has at least 85% identity to SEQ ID NO: 46 andwherein the encoded mut-PPO comprises an amino acid substitution at aposition corresponding to position Leu397 of SEQ ID NO:2 and an aminoacid substitution at a position corresponding to position Phe420 of SEQID NO:2, wherein the amino acid corresponding to position Leu397 of SEQID NO:2 is substituted with aspartate, glutamate, or glutamine, andwherein the amino acid corresponding to position Phe420 of SEQ ID NO:2is substituted with valine or methionine.
 6. The isolated nucleic acidof claim 1, wherein the encoded mut-PPO has at least 90% identity to SEQID NO: 46 and wherein the encoded mut-PPO comprises an amino acidsubstitution at a position corresponding to position Leu397 of SEQ IDNO:2 and an amino acid substitution at a position corresponding toposition Phe420 of SEQ ID NO:2, wherein the amino acid corresponding toposition Leu397 of SEQ ID NO:2 is substituted with aspartate, glutamate,or glutamine, and wherein the amino acid corresponding to positionPhe420 of SEQ ID NO:2 is substituted with valine or methionine.
 7. Theisolated nucleic acid of claim 1, wherein the encoded mut-PPO has atleast 95% identity to SEQ ID NO: 46 and wherein the encoded mut-PPOcomprises an amino acid substitution at a position corresponding toposition Leu397 of SEQ ID NO:2 and an amino acid substitution at aposition corresponding to position Phe420 of SEQ ID NO:2, wherein theamino acid corresponding to position Leu397 of SEQ ID NO:2 issubstituted with aspartate, glutamate, or glutamine, and wherein theamino acid corresponding to position Phe420 of SEQ ID NO:2 issubstituted with valine or methionine.
 8. A plant or plant cellcomprising the nucleic acid of claim
 4. 9. A plant or plant cellcomprising the nucleic acid of claim
 5. 10. A plant or plant cellcomprising the nucleic acid of claim
 6. 11. A plant or plant cellcomprising the nucleic acid of claim
 7. 12. A method for controllingundesired vegetation at a plant cultivation site, the method comprisingthe steps of: a) providing, at said site, a plant that comprises atleast one nucleic acid comprising a nucleotide sequence encoding amut-PPO, wherein the encoded mut-PPO is a variant of SEQ ID NO: 46having at least 75% identity to SEQ ID NO: 46 and wherein the encodedmut-PPO comprises an amino acid substitution at a position correspondingto position Leu397 of SEQ ID NO:2 and an amino acid substitution at aposition corresponding to position Phe420 of SEQ ID NO:2, wherein theamino acid corresponding to position Leu397 of SEQ ID NO:2 issubstituted with aspartate, glutamate, or glutamine, and wherein theamino acid corresponding to position Phe420 of SEQ ID NO:2 issubstituted with valine or methionine; and b) applying to said site aneffective amount of a benzoxazinone-derivative herbicide.
 13. The methodof claim 12, wherein the encoded mut-PPO has at least 80% identity toSEQ ID NO: 46 and wherein the encoded mut-PPO comprises an amino acidsubstitution at a position corresponding to position Leu397 of SEQ IDNO:2 and an amino acid substitution at a position corresponding toposition Phe420 of SEQ ID NO:2, wherein the amino acid corresponding toposition Leu397 of SEQ ID NO:2 is substituted with aspartate, glutamate,or glutamine, and wherein the amino acid corresponding to positionPhe420 of SEQ ID NO:2 is substituted with valine or methionine.
 14. Themethod of claim 12, wherein the encoded mut-PPO has at least 85%identity to SEQ ID NO: 46 and wherein the encoded mut-PPO comprises anamino acid substitution at a position corresponding to position Leu397of SEQ ID NO:2 and an amino acid substitution at a positioncorresponding to position Phe420 of SEQ ID NO:2, wherein the amino acidcorresponding to position Leu397 of SEQ ID NO:2 is substituted withaspartate, glutamate, or glutamine, and wherein the amino acidcorresponding to position Phe420 of SEQ ID NO:2 is substituted withvaline or methionine.
 15. The method of claim 12, wherein the encodedmut-PPO has at least 90% identity to SEQ ID NO: 46 and wherein theencoded mut-PPO comprises an amino acid substitution at a positioncorresponding to position Leu397 of SEQ ID NO:2 and an amino acidsubstitution at a position corresponding to position Phe420 of SEQ IDNO:2, wherein the amino acid corresponding to position Leu397 of SEQ IDNO:2 is substituted with aspartate, glutamate, or glutamine, and whereinthe amino acid corresponding to position Phe420 of SEQ ID NO:2 issubstituted with valine or methionine.
 16. The method of claim 12,wherein the encoded mut-PPO has at least 95% identity to SEQ ID NO: 46and wherein the encoded mut-PPO comprises an amino acid substitution ata position corresponding to position Leu397 of SEQ ID NO:2 and an aminoacid substitution at a position corresponding to position Phe420 of SEQID NO:2, wherein the amino acid corresponding to position Leu397 of SEQID NO:2 is substituted with aspartate, glutamate, or glutamine, andwherein the amino acid corresponding to position Phe420 of SEQ ID NO:2is substituted with valine or methionine.